I ran across the new web-based MSN Messenger the other day.  I haven't had access to messenger from work in a long time.  The old version didn't work through our firewall, so I developed a local proxy to tunnel the traffic.  Then they started blocking that traffic outbound.  Then they rolled out a crappy customized version of it to collaborate in-house which couldn't go outside the firewall.  But this web-based one works perfectly through the firewall, so I am once again available while at work...within reason of course.