http://walletup.com/i/postimg/20100810_143640p.jpg

Hitachi SimpleDrive Mini 320GB USB 2.0 Portable Hard Drive (Blue Dusk) for $24.99 Shipped

Hitachi SimpleDrive Mini 320GB USB 2.0 Portable Hard Drive (Blue Dusk) for $24.99 shipped after code HDDSPECIAL123 and a $10 rebate.  Here is a screenshot for your reference.  It does not require a separate power supply and is also smaller, making it convenient to carry around.  Most places have this Hitachi 320GB portable USB drive for over $60.