After Wiimote for PC/Mac, now we have Sony PS3 SIXAXIS controller for XP!

Claims on the site:
The Sony PS3 SIXAXIS controller can be used on a Windows PC but Windows XP and upwards would be best. It works as USB HID device under Windows.

If you do have a Sony PS3 SIXAXIS controller, please do give it a try!

Links:
DCEmu UK forum – PS3 Sixaxis Controller Can Be Used In Windows!
Crunch Gear – Use SIXAXIS With Your Windows PC