TED.com is simply great, and the presentations are simply jaw-dropping. You will certainly find many good topics and speakers there but I found the following is one of the best (YMMV, of course). Neuroanatomist Jill Bolte Taylor had an opportunity few brain scientists would wish for: One morning, she realized she was having a massive stroke … make the best of your next 18 minutes with this video (with transcript).
http://static.videoegg.com/ted/flash/loader.swf
M.Y. Lessons Learnt 