I can make some suggestions for you from Newegg. It depends on how much storage you want. Here's a Raptor drive that has approx. 74 GB and it is fast, but costly:
Western Digital Raptor WD740GD 74GB 10,000 RPM 8MB Cache Serial ATA150 Hard Drive - OEM
It has a rebate on it now so get it quick if you want it. If you want big storage, I recommend something similar to this. Are you using SATA?
Western Digital Caviar SE WD3200JD 320GB 7200 RPM 8MB Cache Serial ATA150 Hard Drive - OEM
320GB for only $125?!?! Wow....that's after the rebate but still, that's a huge amount of storage for the price. Best drive in terms of storage space to cost.