Google already has a option for downloading videos, but you tube does not. This is an instructable describing on how to download the videos off of youtube to your computer for editing, storing, whatever.
It opens up endless possibilities for example you can take existing videos like this one
and crappily edit them to be like this one
Step 1: Get the software
You also need grease monkey, great software that allows you to control websites http://greasemonkey.mozdev.org/
Once grease monkey is installed you need the youtube extension http://www.joshkinberg.com/blog/files/youtube_to_me.user.js
Step 2: Install the script
When you are done you can go to you tube, making sure the script is enabled, and a red bar with the option to download should appear on the top of the screen. Click it.
Step 3: Opening the .flv file
And voila, you have a usable video ripped from you tube. And all it took was losing your dignity to a monkey.