Cheetah
Deity
I've watched quite a few TED videos, and they still are as fascinating, thought-provoking and explanatory as they were the first time I watched one.
I think my absolute favorite is Hans Rosling shows the best stats you've ever seen. That was extremely educational.

Philip Zimbardo shows how people become monsters ... or heroes is also very enlightening.

I'm sure many people on CFC have watched at least one or two videos from TED.
What do you think about TED? Is there any particular talk that you really liked?