USB Webcam:

  

Logitech QuickCam Express

  

$50

and PC with open USB port

    
     

Advantages:

Cheap
Compact
Easy to install and use

Disadvantages:

Reaches 30 fps only at 160 x 120 pixels
Small, modest quality images
Only real-time capture
No tripod socket
Significant top-to-bottom time-dispersion over each frame at 320 x 240 pixels

Links:

Logitech QuickCam

320 x 240 QuickCam Movie (3034 KB)

160 x 120 QuickCam Movie (2303 KB)