Flock is supposed to be "The Social Web Browser". It does for social networks what Trillian does for IM, ie. makes it possible to access and use various interfaces/sites at the same time, without having to switch in and out all the time.
From their version compare page – Flock offers integration between social sites – Facebook, Flickr, YouTube and Twitter in a sidebar. Webmail integration for Yahoo! and Google mail. Photo and Video Support includes photos and videos from Facebook, Flickr, YouTube, Photobucket, Truveo and Picasa (AWESOME!). It allows you to post favorites to del.icio.us and ma.gnolia. As if all this wasn’t enough, it also supports multiple blog platforms, you can compose and post blogs to Blogger, Blogsome, LiveJournal, Typepad, WordPress, Xanga and self-hosted blogs.
I am ready to kick the tires and take it for a spin, will keep you updated on what I find out. Stay tuned for more details.