This Seagate FreeAgent GoFlex Desk sounds like an exercise commandment for your desk, but it's the world's first 3TB external hard drive. Best news: It has USB 3.0 and FireWire 800 (along with USB 2.0).
The drive itself ships with USB 2.0 adaptor for $US250, and you can get the USB 3.0 and FireWire 800 separately (not sure for how much). And it has a built-in NTFS driver for Macs so you can read and write to Windows NTFS-formatted drives. [Seagate]