You need either an IP Network camera or a USB webcam. For more details on
buying a webcam click here.

The following is a list of tested and approved USB cameras:

Logitech
QuickCam® Orbit MP
QuickCam® Pro 5000
QuickCam® Communicate STX

Creative Labs
Live!
Live! Cam Video IM

Microsoft
LifeCam VX-3000
LifeCam VX-6000