It's been a while, watched 2 days ago, like these:
That artificial bird actually flies very well
http://www.ted.com/talks/a_robot_that_flies_like_a_bird.html

I like his style, his voice and the way of presenting is very attractive
http://www.ted.com/talks/kevin_slavin_how_algorithms_shape_our_world.html

A very interesting alternative to Wifi (won't think it will be as widely useful)
http://www.ted.com/talks/harald_haas_wireless_data_from_every_light_bulb.html

I really like the topics there.