Here are some of the science channels I like on youtube.
History: Horrible histories - short and hilarious clips from the BBC children’s series.
Chemistry: Periodic videos - short episodes covering 1 element at a time.
Physics (mostly): Sixty Symbols - short episodes covering 1 symbol at a time.
Astronomy: SpaceRip - Just cool space videos
General science: SpiralOut11235 - all kinds of documentaries.
General stuff: TED - TED talks by scientist, artists and interesting people.
Not on youtube, but Fora.tv has some very interesting stuff too.
I moved away from the TED.com site when it started crashing my Firefox/Linux browser about a year ago. Seems to work fine now, though I think they still post all their videos on youtube too.
By the way: which video is the spaghetti sauce one?
Yup, that’s the one. The same guy also wrote this article on ketchup, and why, despite people trying to introduce multiple varieties, plain ol’ Heinz rules the market. Sort of the opposite of the spaghetti sauce conundrum.