As expected, the DriveStation HD-HXU3 is the first external USB 3.0 drive in the U.S. It promises transfers up to 4.8Gbps (compared to USB 2.0's 480Mbps) and Buffalo has a two-port USB 3.0 PCI Express card to get you started.
There's no price yet on the USB 3.0 PCI Express card (IFC-PCIE2U3), but it's expected to be about $60. The drive itself will be $200 (1TB), $250 (1.5TB), and $400 (2TB), and ships with Memeo AutoBackup software for the Mac or PC. [Buffalo]