ted.com has some of the coolest, most interesting, flat out fascinating webcasts I've ever seen. Get a bunch of smart, talented people together and see what happens. What a great concept! This guy's 37 minute juggling/learning/space/art/motion/rhythm segment is mind-blowing.
Actually, most of the stuff on the ted site probably can't be considered a waste of time-- it's too informative and useful! But it is a great way to spend some time.