Normally ON Switch using N-CH MOSFET and pull-up resistor
Yes, that's perfectly valid (should be a base resistor on the BJT, of course). 

Another method you might use could be to use a P-channel MOSFET with a pull-down resistor (just the complement of your circuit). However this does not work if the power is removed from the micro since the protection circuit will drag down the output pin. Your circuit also allows the micro to switch a higher voltage than its supply (for example a 3.3V  output switching a 5V or 12V circuit). 

Edit: Added are two additional circuits- one using another NPN transistor which will work with power removed from the micro and using an opto as you suggested. Both are high-side switches and the opto one adds isolation while actually simplifying the circuit. 







simulate this circuit &ndash; Schematic created using CircuitLab

A third approach is to use a depletion mode MOSFET or a JFET but that's a lot trickier because you have to come up with a negative voltage to turn the transistor off. It does work in the absence of any significant voltage supply though. Another disadvantage is that power devices are unavailable in P-channel type.