While having full power control of your Raspberry Pi, meaning a power on/off button would be great a quick and easy thing you can do is add a reset switch. If you have the Rev 2 version of the Pi, (the one with mounting holes) apparently there is an un-populated header labeled P6. By soldering a momentary switch to those points, or a cleaner approach is to put a removable header in that spot.
Once you have the header in place you can either momentarily touch the two leads together to cause a reset (just like a PC reset button) or fashion a momentary button with a female header. If you have some old PC junk laying around you might be able to salvage the reset button from a pc (that acts the same way on a pc motherboard) as the author of the article did.
Not really much to it, but useful. Full write-up here.