Overclocking

So. Recently I was looking at overclocking, and I overclocked my graphics card (XpertVision Nvidia Geforce 7600GT) from it's stock speed of 560Mhz (Core clock) and 700Mhz (Memory clock) to 700/801, raising the temperature by about 5 degrees C.

Does anyone here overclock their hardware at all? If so, what do you use to do so, and do you add any extra cooling?

I only overclock my gp2x. It's safe to go from 200mhz to 275mhz on mine. Dunno if it's the same for GPUs.