This 320GB external drive from Iomega supports both USB 2.0 and eSATA, the external SATA interface that many newer model desktops and laptops are starting to ship with. The benefit of having an eSATA drive over regular USB is the speed. eSATA is as fast as internal SATA, but you can plug and unplug it like a standard USB device.
The drive costs $239.95 and comes with a eSATA PCI card to place into your PC.
Product Page [Iomega]