Seagate FreeAgent GoFlex Pro FireWire 800 USB 2.0 Ultra-Portable External Hard Drive for Mac for $119.99

The GoFlex Pro for Mac ultra-portable drive is formatted for Mac out of the box, making it fully compatible with Time Machine software. It has a 7200RPM drive, which takes full advantage of FireWire 800. Install the downloadable HFS+ driver on a PC, and the drive can be used interchangeably on both Mac and PC computers without formatting. This is the perfect solution for primarily Mac computer users who still regularly utilize their PC.