The first thing you need to buy is a webcam. I personally recommend a Logitech Quickcam Pro 4000.
Once you have the webcam, you need to buy the servo motors and the phidget device. I recommend getting the 4-Motor PhidgetServo Kit. http://www.phidgetsusa.com/viewproduct.asp?SKU=2001
For the Pan and Tilt you should buy the Servomotor X-Y Axis Mount from Images SI, Inc. http://www.imagesco.com/catalog/motors/s_access.html
Next, you need to get a Project Enclosure so to mount the camera and motors on. Also the Project enclosure will hold the Phidget device. I just picked up a plastic one from radioshack. http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=270-1803
The last thing you should buy is a anti-slide sheet. You can get one from shopco or wal-mart in the car department. It just prevents the motors from tipping over if they slide too fast.