Downloading YouTube Videos
This is a site that has a script for downloading YouTube videos. There is also a script for Google Video, but it's no longer necessary because Google video has that functionality available (for free videos).
I haven't figured out how to install this, but it's nice to know I can keep good videos I find. Especially since many YouTube videos will vanish as copyright issues get more pronounced.
P.S. I can't vouch for the integrity of this script. Use at your own risk.