Buy.com - Cavalry 500GB 7200RPM USB 2.0 & eSATA Dual Interface External Hard Drive for $99.99 after Rebate, Shipped Free!:
Offer: Nice deal even without the rebate. This Cavalry 500GB external hard drive has a 7200 RPM spindle, but the best part is the dual interface. It works with USB 2.0 or the new eSATA interface for really fast transfer rates. I have a Cavalry myself and it's been very reliable and quiet. It does tend to get warm because it uses the case as a heatsink (which is why it's quiet). Just make sure it's not buried underneath anything.