References for MOSFET as a switch for LED/Laser Diode
Here are some of the things that hepled me the most.

MOSFET as a switch:

I initially started messing around with electronics with a solderless breadboard, a bunch of old RadioShack parts, 555 timers and transistors, dacs and such.  Most of my projects thus far have been working on voltage regulator and PWM circuits with LEDs, and I ended up moving to MOSFETs over transistors as an easier to use switch, with better operating characteristics than certainly any of the transistors I've had available to date.  MOSFETs are voltage rather than current controlled, and it's extremely nice not to have to run a crapton of current from a logic circuit just to keep a switch turned on.  Mosfet drive currents can be substantial (surges of 1.5, 4, even 25A for tiny pulses), but for my projects they don't even compare to running many milliamps or having to construct darlington arrangements just to switch a few amps of current.

Operation:
The operation description I eventually settled on for how a MOSFET works is a switch or relay that is controlled by charging and discharging a capacitor.  The device is voltage sensitive, but I find it easier to keep in mind that it is sensitive to the voltage that the gate capacitor has been charged to, more than the voltage that is applied to the gate.

N-Channel vs P-Channel

Without getting into the semiconductor properties or physical makeup, N-Channel MOSFETs operate by applying a positive voltage from the gate to the source, and are placed between the load and the negative wire of the loop in question.  P-Channel MOSFETs operate by applying a negative voltage from the gate to the source, and are placed between the load and the positive wire of the loop in question.  

N-channel MOSFETs tend to have much lower gate capacitance than comparable P-channel devices.  These differences are because of the way the semiconductors have to be physically built.  Also because of fundamental differences in the way they are built, MOSFETS that must be N+P matched and paired for one characteristic (slew rate, ON resistance, switching speed) will by necessity vary widely in all of their other characteristics.  I've not tried, but I understand that this makes selecting a matched N+P MOSFET for something like audio signal amplification somewhat more complicated than it might be for finding a matched N+P transistor.

Enhancement vs Depletion

N-channel enhancement mode MOSFETs operate as a normally open voltage controlled relay, closing the circuit when the gate voltage is brought sufficiently above the source.  

N-channel depletion mode MOSFETs operate as a normally closed voltage controlled relay, opening the circuit when the gate voltage is brought sufficiently above the source.

P-channel devices operate the same, except that the gate voltage must be brought below the source.  

Unlike a transistor, a MOSFET in it's ON state is rated by it's Rds On, or on state resistance, rather than having a rated voltage drop in the on state.

Off state resistance is very very high, Meghohms to Gigaohms.  On state resistance varies with design intent, from fractions of milliOhms to thousands of ohms.  Generally speaking lower on state resistance is better.

VDss - Drain to source voltage:  This is the voltage that the MOSFET is rated to block.

Id - Continuous drain current - the current the MOSFET is rated to conduct, rated either by ambient temperature or junction temperature.  Substantial heat sinking and or active cooling may be required for some MOSFETs to operate at this current level, and relevant information can be obtained from the datasheet.

Drive Voltage - The voltage at which the gate of the MOSFET is intended to be driven.  Note that a MOSFET will only reach its rated Rds On when driven at the rated voltage.  Many can be driven below the rated voltage, resulting in a higher, but still usable Rds ON, and some can be driven substantially above the rated voltage.  The rated voltage is usually just above the "knee" of the MOSFETs transfer characteristics graph.  You can get drive voltages much lower than the rated blocking voltage of the MOSFET, right down to logic level gates. 

Vgs(Max) - the actual maximum drive voltage.  Be careful when mixing mosfets!  One mosfet that turns ON at 5V might have a lower max gate voltage than another, 

Power Dissipation(Max) - This is the amount of power the mosfet can survive dissipating itself, when adequately cooled.  One way to look at it is that your combined switching and conduction losses for that switch must absolutely be below this threshold.

Operating Temperature - MOSFETs tend to have really nice operating temperature ranges, so I've never concerned myself with this for a MOSFET.  I live in Canada, so for any other component it's one of the first things I check.

You can get them in a wide variety of thru hole and surface mount packages.  One thing that surprised me was that some of the surface mount chips, despite being tiny, had fantastic ratings.  I think this is because newer tech is tending to come out only in newer packages.  I've been unable to find really good tiny through hole MOSFETS, but specs on some of the 3mmx3mm surface mount chips can be pretty great.

Losses - You'll have conduction losses and switching losses when operating a MOSFET.  

Conduction losses are the regular I^2R losses occurring as current flows across the MOSFET in it's On state.  These can be reduced by selecting a MOSFET with a lower Rds ON property, and of course reducing ohmic losses in the rest of the circuit.

Switching losses are the losses that occur while the MOSFET is changing between it's On and Off state.  Because during this time, the MOSFET has a higher resistance, but is still conducting, a much higher portion of the energy delivered to the MOSFET is turned to heat.  This can be reduced by causing the MOSFET to transition between states more quickly.  This is where it pays to remember that the MOSFET is switched by charging the capacitor of the gate, not just by applying voltage.  If you charge the capacitor more quickly, the MOSFET will switch more quickly.

To this end, MOSFET drivers exist, providing a convenient way to switch MOSFETS much faster, and at the same time take care of level shifting when, for instance, you want to use a MOSFET with a 10v gate drive voltage and +/-20V Vgs(Max), but you want to control it with a 5V 555 timer circuit or a 3.3V microcontroller.

Probably my favorite thing about MOSFETS is that they don't specifically require a gate resistor.  One less stupid resistor.  That being said, at higher frequencies (and I believe higher switching currents too), sometimes a gate resistor is used to dampen inductive-capacitive ringing on the gate.  This is where some (likely parasitic) inductance in the gate drive circuit starts resonating with the capacitor that is the gate, causing it not to maintain it's intended state perfectly.

Generally speaking, Mosfets are considered best for low voltage, high current operation.  The lower the voltage and current the more likely a transistor might be an acceptable option, and the higher the voltage, the more likely a switch must be made to an IGBT.

Advances have been made in the way that the physical semiconductors of MOSFETS are built with every generation of MOSFETS invented.  Massive efforts have been made to bring P-channel devices closer to N-channel devices, particularly in gate capacitance at similar other properties.  This discrepancy is caused by the lower mobility of P charge carriers.  P-channel devices may be expected to have 5x the gate capacitance of N-channel devices.

Also as a result of this, special MOSFET drivers have been invented for the purpose of driving N-channel MOSFETS on the P side of the load.  This is done by boosting the N gate voltage up as necessary above whatever the source voltage happens to be and cause it to turn on.  These drivers typically have lower rated current (Often 300mA instead of 1.5A in a similar package) it seems, but this would be compensated for by the much lower gate capacitance.

So now you get to make yourself a circuit to switch power to an LED or a Laser Diode.  That's going to be pretty easy, you can pretty much pick a MOSFET and wire it up with the information above, but for the sake of some perspective on how your MOSFET's characteristics will matter, lets consider your loads.  

Ok, so they're both diodes!  Electrically, they're more or less the same thing.  They're fairly robust in terms of microsecond voltage and or current surges, but at the same time if you overheat them or run more than rated current or voltage for larger fractions of a second it's not hard to find out how much smoke they have inside.  A laser diode is an LED and usually optics designed to produce coherent and usually collimated light.  For our purposes here, I'll just call them both LEDs.  LEDs have a negative thermal coefficient, meaning that as they heat up, their resistance decreases instead of increasing, making them prone to current runaway, a state where the current flowing through the LED becomes enough to raise it's temperature enough to lower resistance enough to increase current and raise temperature...  This loop continues if not held in check until the LED burns out.  As a result, thermal design and voltage/current control are important for LEDs.  In your case you will probably want to use a current limiting resistor (just a resistor in series with the LED) sized to regulate the LED to it's intended current.  In order to have a matched thermal coefficient to the LED, these resistors often burn off just as much energy as the LED.  You can also use this resistor effectively as a slow blow fuse.  Thin film surface mount resistors are often set at a power level so that if a module (something like an LED puck for interior lighting) receives the wrong voltage (24V instead of 12V, etc) the resistor will burn out and break the circuit before the LED is damaged, making the repair much cheaper and easier

Personally I hate using resistors, especially if the LED is dissipating substantial power.  That said, one other advantage to them is the way that they drop the voltage.  A resistive load in series shares and provides a steady voltage to an LED in series, and LEDs, while they are robust for PWM purposes, perform at higher efficiency levels at a steady voltage.

For instance I have a 3W RGB LED, and one of the first projects I did was fading the LEDs on and off 0 to 100% at different rates with a "breather" circuit.  I used 7-9v PWM(Pulse width modulation, rapidly switching the circuit all the way on and off), not current controlled to drive the LEDs.  Because I simply adjusted the max PWM levels to the max brightness of the LEDs, they didn't burn out, but they got unnecessarily hot.  Since then I've learned that the efficiency response of an LED is determined by their instantaneous voltage, and running 2.3 and 3.3V LEDs at 9V makes them pretty inefficient, so a more complicated driver is necessary, and I'm working on version 3 or 4 of that now.  My point is, although a series resistor can waste just a silly amount of power in a high power LED circuit, some of this is mitigated by the efficiency of the LED if whatever other voltage regulation you use is inadequate.  

This is where you'll probably end up in a few weeks or months, and it's where MOSFETS shine.  To take 9V and give an LED a smooth 3.3V without wasting too much power, you need to use an inductive/capacitive filter.  Instead of switching the current directly through the LED, you switch the current through an inductor to charge a capacitor and put the load in paralell to the capacitor.  

Having a higher inductance or a higher frequency will give you a smoother output with less ripple.  Higher inductance means a bigger coil, and you also want low resistance, which means the coil has to be of larger wire.  Because increasing the frequency will let you get away with a lower inductance, which lets you use a smaller coil with lower resistance, the speed at which your switch can operate becomes a major performance factor for your overall circuit design, and MOSFETs are fast.  The smaller the gate capacitance and the faster you charge it, the faster it switches.

For my project, I need two stages of switching.  One stage to regulate voltage for a particular color of LED.  This stage I need or want to run at the highest frequency possible and I'll want to be very careful about component selection.  The second stage is to PWM switch the correct voltage through the LEDs at a 0-100% duty cycle.  Because humans can usually see no more than 150-200hz, I'll want that signal to be at least 200hz, and possibly up to 1000hz, although I don't want to go too high, as at high enough frequencies, the tiny inductance in the wires going to the LEDs will start to matter and corrupt the PWM signal.

It's quite a bit of effort to get rid of a few resistors, but when the resistors are often using close to the wattage of the LED itself, the potential benefit is clear. Compared to transistors, using MOSFETs has greatly simplified the design and logic control parts of this circuit, especially since part of my obsession is efficiency.