DownloadableYouTube
This is a bookmarklet to make all link from YouTube search result downloadable.
How to use
Bookmark this link. (Right-click the link and add to bookmark.) And then click the bookmark on a search result of YouTube. So all links change not to a browse page but to a download cgi. You can save the movie with right-clicking them and choose "save as..".
How to see the downloaded files
The format of those movies is *.FLV (Flash Movie), so you need a flv player. If you don't have it, get "Free Riva FLV Player 1.2" from Riva VX: Downloads.
How it works
An URL like "http://www.youtube.com/watch?v=********" is a page to browse movie. The bookmarklet replace all url like above to like "http://youtube.com/get_video.php?video_id=********". It is a cgi to get movie.
I made this on a Firefox, and I didn't check its behavior on IE.