Video download from video site such as youtube.com has many methods, there are allready many software downloader , online url conversion utility to do the job, however, using userscript is a better way is you have already installed browser-addons.

• Video Link Grabber
  This script puts a link at the bottom of the page with the location of the stand-alone video-player of a lot of sites (see tags). Can be used to copy/paste into forums... You can also click on the link to view the video fullscreen.

  FireFox: http://userscripts.org/scripts/show/9147
  Internet Explorer: http://iescripts.org/view-scripts-78p1.htm
  

• Video Downloader
  A video download utility powered by videodownloader.net http://javimoya.com/blog/youtube_en.php . Video Downloader allows you to download videos (to your computer) directly (and easily -just one click-) from most video sites. You can download from: Angry Alien, Blennus, Blip.tv, Break.com, Dailymotion, Double Agent, eVideoShare, Free Video Blog, Google Video, Grinvi, iFilm, Keiichi Anime Forever, Metacafe, MySpace, MySpace Video Code, Putfile, Totally Crap, vidiLife, vSocial, AnimeEpisodes.Net, Badjojo, Blastro, Bofunk, Bolt, Castpost, CollegeHumor, Current TV, Dachix, Danerd, DailySixer.com, DevilDucky, Double Agent, EVTV1, FindVideos, Hiphopdeal, Kontraband, Lulu TV, Midis.biz, Music.com, MusicVideoCodes.info, Newgrounds, NothingToxic, PcPlanets, Pixparty, PlsThx, Revver, Sharkle, SmitHappens, StreetFire, That Video Site, VideoCodes4U, VideoCodesWorld, VideoCodeZone, Vimeo, Yikers YouTube and ZippyVideos.

  Internet Explorer: http://iescripts.org/view-scripts-52p1.htm
  

• Video Download
  Save video clips from YouTube, Google Video, Myspace, Metacafe, Break.com, Putfile, Dailymotion and Sevenload. The script shows a small notice-bar at the top of supported video-pages. Upon clicking the notice-bar download links are shown on a small results page. Right-click to save the files. Results page and images are part of the script and not loaded remotely.

  FireFox: http://userscripts.org/scripts/source/8427
  FireFox: http://userscripts.org/scripts/show/4037
  Internet Explorer: IE7Pro user scripts(default installed).
  

• Youtube Video Download
  FireFox: http://userscripts.org/scripts/show/8177
  FireFox: http://userscripts.org/scripts/show/7880
  FireFox: http://userscripts.org/scripts/show/3982
  Internet Explorer: http://iescripts.org/view-scripts-3p1.htm
  

• Google Video Download
  FireFox: http://userscripts.org/scripts/show/5821
  

• Metacafe Video Download
  FireFox: http://userscripts.org/scripts/show/4316
  

• LiveLeak Video Download
  FireFox: http://userscripts.org/scripts/show/6442
  Internet Explorer: http://iescripts.org/view-scripts-71p1.htm
  

• 6Rooms Video Download
  Internet Explorer: http://iescripts.org/view-scripts-72p1.htm
  

• Tudou Video Download
  Internet Explorer: http://iescripts.org/view-scripts-73p1.htm

• RedTube Video Download
  FireFox: http://userscripts.org/scripts/show/8691
  Internet Explorer: http://iescripts.org/view-scripts-61p1.htm

• XTube/Pornotube Video Download
  FireFox: http://userscripts.org/scripts/show/5208
  Internet Explorer: http://iescripts.org/view-scripts-62p1.htm