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GetTubeVideo is high performance online video download manager that lets you get most every video on the web. GetTubeVideo allows you to download videos directly to your computer from most online video sites and automatically convert it to variety of video formats.

GetTubeVideo features:

• Download videos from YouTube and XTube kind sites
  
• Extract audio from YouTube kind videos
  
• Extract audio from any video file
  
• Convert any video file between all popular video formats (3GP, ASF, AVI, FLV, MOV, MP4, MPEG, WMV)
  
• Convert any audio file between all popular audio formats (MP3, OGG, WAV, WMA)
  
• Ability to setup width/height of encoding video

List of the most popular supported sites:

• youtube.com
  
• video.yahoo.com
  
• myspace.com
  
• metacafe.com
  
• dailymotion.com
  
• video.google.com
  
• hi5.com
  
• archive.org
  
• badjojo.com
  
• bangbros.com
  
• bebo.com
  
• blip.tv
  
• boysfood.com
  
• break.com
  
• broadcaster.com
  
• buzznet.com
  
• camelstyle.net
  
• crunchyroll.com
  
• dachix.com
  
• gametrailers.com
  
• gofish.com
  
• heaven666.org
  
• ifilm.com
  
• imeem.com
  
• kaktuz.com
  
• lifeout.com
  
• liveleak.com
  
• livevideo.com
  
• megarotic.com
  
• megavideo.com
  
• mtv.com
  
• multiply.com
  
• netlog.com
  
• peekvid.com
  
• perfspot.com
  
• photobucket.com
  
• pornotube.com
  
• redtube.com
  
• revver.com
  
• ringo.com
  
• rude.com
  
• sexyandfunny.com
  
• sexyclips.org
  
• sidereel.com
  
• smog.pl
  
• sports.espn.go.com
  
• tagged.com
  
• uncutvideo.aol.com
  
• xtube.com
  
• youporn.com
  
• yuvutu.com
  
• zedge.net

More Information & Download

[DigeratiPrime]

I've use the AIO Video Bookmarklet to download the Flash Video files (flv) directly and watch them in Media Player Classic (mplayerc.exe) directly (with FFDShow installed), no transcoding needed.

As for extracting the audio there FLV Extract.

[tain]

There is a list of such things over here.