I love TED talks. Sometimes I’ll spend hours watching the videos on the site. Check out this cool video on ‘Underwater astonishments‘.
From the description:
David Gallo shows jaw-dropping footage of amazing sea creatures, including a color-shifting cuttlefish, a perfectly camouflaged octopus, and a Times Square’s worth of neon light displays from fish who live in the blackest depths of the ocean.

Yeah, that was a great one.
Not reef related, but a couple of my favorites are the Dan Dennett (On Dangerous Memes), Richard Dawkins, Brian Greene & Wade Davis…
Man, I waste many an hour in the office on that site lol.