Ezthumb - A video thumbnail generator based on ffmpeg.
Video Thumbnails Maker - Allows you to make thumbnails (caps, previews, screen-lists) and screenshots of video files.
Thumbnail me - Thumbnail me is a free and open source thumbnails generator built on the movie thumbnailer binary.
MoviePrint - MoviePrint lets you create screenshots of entire movies in an instant.
Scenegrabber.NET - Scenegrabber.NET provides an easy way to create sceneshots from movie clips.
Thumbs - Thumbs is your new personal assistant for movie stills and thumbsheets.