http://www.rockmelt.com/
Marc Andreessen's new project (Netscape founder), a chromium-based browser with an emphasis on social networking and super-fast searching.
At first I thought this is only going to appeal to die-hard social networkers. But I can't help but wonder if we aren't going to see more of these features built into more mainstream browsers before long though if this catches on.
Of course it doesn't appear to be offering anything you can't get with a few plugins/extensions, but it's a select few who really use plugins and extensions.
Looks interesting, if for no reason other than its unique take on the UI (compared to today's mainstream browsers).