I’m really excited about ubiquity: http://labs.mozilla.com/2008/08/introducing-ubiquity/ is definitely worth a few minutes if you care about where the web is going.
I loved Aza Raskin’s Enso launcher and wrote a few commands for Enso 2 prototype but it was too buggy to use. I envy mac users because they have quicksilver.
But now Aza, being the head of user experience in Mozilla Labs, has found a perfect place to push his ideas forward: firefox, the best cross-platform browser.