A friend of mine sent me an email a couple of days ago about meebo.com. So I went and checked out the website and was pretty amazed by the service they offered. Although still an alpha version, it provides easiness to login to multiple IM (instant messaging) accounts, like Yahoo!, MSN, Jabber and AIM/ICQ. The connection was very very stable. Some of you guys may not be able to use the Yahoo! Messenger from the office, some are even unable to install the software itself. Guess this might be the solution to your problem (unless meebo.com is restricted as well, that is :P).