Strixx.org.uk provides a tool that searches Google Video for all playable clips and displays the results as a page of thumbnails. This is useful when you want to visually scan many results (thumbs) within a search topic. I’ve found it to be a surprisingly effective way of revealing information even though there are no immediate textual clues. For example a search for your favourite football club, "singer" or events will display a pool of images that you can choose from based on the immediate visual content contained in the frame.
This page performs a search on video.google.com and returns only those results which are directly playable in the browser. All result pages are processed, queries with a lot of matches (max 1000) may take up to a few minutes to process. Requires Google Player.