I've been using this nifty little feature within Safari lately, for keeping all those cool YouTube vids on offline storage

1. Download and install Safari, if not already installed.
2. Browse to your desired Youtube video page.
3. Whilst the clip is loading press Command-Option-A (Mac) or Control-Alt-A (Windows), this opens the browser's activity window.
4. In this window you'll see all the individual page objects loading, including one with a much more substantial size loading in the Status column (eg. 357k of 17.6MB)
5. Now double click on the address line to save the video to your hard drive, easy!
6. You might want to rename the flash video files to something more identifiable, as aposed to the default 'videoplayback.flv'
Sick browser trick for rippin them videos