I've been playing around with me.dium, the latest and greatest in social browsing technology. GigaOM has already reported on it (see also here and here) so I won't bore y'all with the gory details. I do wonder how well it will scale, though, especially if you're eventually able to import or integrate with your existing buddy list instead of setting up Yet Another Buddy List (YABL!) in me.dium. Heck, I have 1300 people in my Jabber roster and I don't know that I want to co-browse with them all... :-) I'm sure the good folks at me.dium are thinking hard about the problem.
BTW, if you're really interested in playing with me.dium, Jabber me with your email address and I'll see if I can send you an invite (don't email me, I still have 1500 messages in my inbox and I don't need more!).