ImageGrab is a nice utility aimed at extracting images from all kind of videos, also from Video CDs or SVCDs, and even from live video streams which are delivered to the computer by a webcam, a camcorder or an analog video capture card. It is a freeware image grabbing application.
Here are some screenshots to illustrate the features and user interface of this application:
PicPick
WinCam
SmartCapture
HyperSnap
Snagit