Given a YouTube or Vimeo URL, downloads the underlying video file, with a sensible file name. It downloads the highest resolution version of the video available: first it tries HD MP4, then regular MP4, then WebM, and finally FLV. It also works on playlists, and works as a bookmarklet[doesn't exist] to download the video you're watching.
Since a regular web page for Vimeo won't give a proper upload date, because the developers are fucking insane, I learned how to do it another way.
Get the video ID from the URL, then get its XML information and find
e.g. for Codehunters - (2006 movie):