Flock

Flock claims to be a new kind of 'social' web browser, integrating popular web services (Flickr, Blogging tools, social networking sites, etc.) into your browsing experience. It's based on Firefox, made by a bunch of ex-Mozilla guys, and by the looks of it, there's a lot of interest, (mainly from the blogging community) considering it's only a private beta release at the moment.

Flock Site

Wired News Article