LiPo 3S 11.1V Power Regulator
It's not the motor specs that matter, assuming you're happy with how it runs from your 11V source.  The issue is how much current this FEZ thing needs at what voltage.

A linear regulator should work well enough as long as the motor doesn't temporarily make the 11V supply dip so low that the regulator can't maintain the output voltage anymore.

In theory, a regulator puts out a constant voltage as long as the input voltage is above some threshold.  If you're trying to get 5V or 3.3V, then 11V is plenty in that regard.  However, in reality regulators can only cope with a certain speed of input voltage change.  Motors can cause large and sudden spikes, which can get onto the regulated output to some extent even if the regulator input stays above its minimum threshold.

Fortunately the solution to both problems is simple.  Put a diode followed by electrolytic storage cap between the 11V supply and the regulator input.  That will prevent negative going spikes from making it to the regulator input.  The capacitor will hold up the regulator input voltage for the short duration of any spike.

In a generally noisy environment like what you describe, it's a good idea to put some high frequency filtering in front of the regulator.  I don't know how much current this FEZ thing draws, but if its just a micrcontroller at let's say 200mA, then a ferrite bead or "chip inductor" followed by 10uF ceramic cap right accross the regulator input and ground terminals will do fine.  This will attenuate the high frequencies that the regulator is not so good at dealing with.

Another point is that a linear regulator will be rather inefficient in this application.  Even if this FEZ thing wants 5V, that's still 6V it will drop for about 45% efficiency.  That by itself may not be a big deal since the power wasted as heat may be small compared to what the motors use.  It's probably more a issue of dealing with the heat.  Again, that depends on the specs of the FEZ.  If it draws 50mA at 5V, then the regulator will only dissipate 300mW.  Not a big deal for a TO-220 case in free air.  If on the other hand it draws 400mA at 3.3V, then the regulator will dissipate over 3W, which needs to be specifically dealt with.

It might therefore be worth looking into a switcher.  At 80% efficiency it would only dissipate 330mW with 400mA at 3.3V out.