Online YouTube downloaders like download-youtube-videos.org, keepvid.com, savevid.com, keep-tube.com have stopped working recently. Some of them ask you to copy the source of the page... well you can do that unless you're as lazy as me

Others offer you some kind of software, and sometimes it is not even freeware. For example, KeepVid offers a commercial program for downloading YouTube videos!
There are many YouTube downloaders that still work. For example,
Replay Media Catcher can download YouTube videos for FREE, freeware
Freecorder 4 and
Jaksta Free Media Recorder can save youtube videos, freeware Firefox extension
Fast Video Download can download youtube videos for free, .... Forget about KeepVid, there are many other ways to download YouTube videos for FREE!
See the following thread for more:
YouTube video downloaders: How to Record/Capture/Download flash videos from YouTube