ClipGrab doesn't only allow you to download videos from sites like Youtube,
Dailymotion or Vimeo but also gives you the ability to convert them in a single
step into "usable" formats like WMV, MPEG or MP3. So you'll be able to watch
(or listen to) your favourite Youtube clips wherever you are.
ClipGrab currently supports these sites:

-YouTube
-Dailymotion
-Vimeo
-MyVideo
-MySpass

WWW: http://clipgrab.de