Videopian is a PHP class that allows you to get any kind of information (such as title, description, author, duration, or flash player URL) about a video hosted on a video sharing service, just by its URL. The currently supported services are Blip, Dailymotion, Flickr (API key required), Google Video, Metacafe, MySpace, Veoh (API key required), Vimeo, and YouTube.
Movgrab is a command-line movie downloader for sites like YouTube. It has no dependencies; everything that's needed should be there in the tar.gz package. Movgrab can connect through an HTTP proxy, can output the download to stdout for piping into another program, and can fork into the background to free up the console. When forked into the background, its progress can still be seen in a ps list.