Keepvid allows you to download videos from a large list of streaming video websites including: Youtube, GoogleVideo, Angry Alien, ArtistDirect, Blastro, Blennus, Blip.tv, Bofunk, Bolt, Break.com, Castpost, Current TV, Dailymotion, DevilDucky, FindVideos, Free Video Blog, Google, Grinvi, Grouper, Hiphopdeal, iFilm, LuluTV, Metacafe, Midis.biz, Music.com... and many more.
Download options are reduced and they are limited to choose the download format when the video allows it. Sometimes you'll be able to download videos as mp4, but most times you can download videos only as FLV.
KeepVid is very useful if you want to download any video from Youtube, Metacafe or any similar website. You only have to copy the URL and paste it in the text box in the upper side of KeepVid and press Download. You'll have the video downloaded automatically.