Want to have your mind blown, slightly? Try this:
• Open any YouTube video
• In the video's URL, switch out the "Y" in "Youtube" for a 3
• Ask yourself why you didn't think of this first.
KickYouTube handles video downloads in an equally clever way, and with even more options. [Lifehacker]
DISCUSSION
There's also this add-on for Firefox, which, so far, has never failed me.
[addons.mozilla.org]