If your Motherboard supports SATA and your interested in fast access times, then take a look at the Western Digital Raptor drive.
It has a smallish capacity and is expensive for the size, but at 10k RPM its nice and speedy.
If your motherboard does not support SATA, stick with what the others said.
Either a Maxtor Diamondmax or a Seagate Barracuda, both give good performance for their price.
Be not afraid of growing slowly, be afraid only of standing still - Knowledge will get you somewhere, stupidity will get you nowhere