These are just a few options. It depends a lot on what you want, how much space, how it will be used, what interfaces you need, whether you need redundancy, etc. I just picked up a 750GB WD MyBook Home Edition (USB2 + FW400 + eSata) on clearance at Best Buy for $162 because it was too good a deal to pass up. I use a 500GB WD MyBook Essential Edition (USB2 only) at work and love it; very quiet, small, and works great with Time Machine and SuperDuper! (I have 2 partitions). If you need something faster and rock solid look at the G-Tech drives. If you need RAID look at Guardian Maxximus from macsales.com