YTD Video Downloader
In the studio, it's often necessary to download videos for use on certain projects. I have found a product called YTD Video Downloader and it works great. Also, if you're only interested in the audio, it will convert the track to MP3, or a whole host of other formats.
The program is freeware, and as you download it, make sure to de-select the add-ons. Also, be careful to scan your system to make sure it hasn't gone ahead and changed your home page or something. (I found no problems, but I am aware of issues with some freeware.)
It works with YouTube, Vimeo, and Blip TV, among others I'm sure.
CNet's download link. Also, the example video from CNet.