http://www.pidgin.im/ I have to also vote for pidgin, which is an open-source (free and community supported) multi-chat program. I use it myself, and it allows you to combine everyone from: AIM Bonjour Gadu-Gadu Google Talk Groupwise ICQ IRC MSN MXit MySpace IM QQ SILC SIMPLE Sametime XMPP Yahoo! Zephyr. In my experience the link to QQ has often had problems. However, I still think it's the best solution for the multi-chat protocol problem. In general I just load up Pidgin and Skype. In China, I imagine you might still load up QQ as well. Otherwise, try to persuade your friends to just stick to one network!

One reason I like Skype is because it does not seem to have the big "footprint" that so many of Microsoft's products have. In other words it does not take up so many resources of your computer. It works well, and has good features to remember chat histories. The only other one I use is Yahoo Messenger, but I use the one on the web, so I do not have to install it locally. It works fine, but I still prefer Skype. Also Skype does not do the "heavy-handed" approach of ushering you down a certain path or their choosing. It seems to respect your volition more than Microsoft does.

you can also try 'trillian'. check which of these supports most of your accounts... I dont think any of these support qq or fetion, but they all support msn, skype, facebook! they can be of sm use

You can try ebuddy or imo.im It is web based, so it is pretty light on your machine. No installation required BUT it does not support QQ and other chinese chat clients. As for QQ, you can consider Web QQ. @Peachey: I will try pidgin

I used an online multi-chat client a couple of years ago... hmmm it was OK but I think the site is gone now. I just found www.pidgin.im on a search, not the perfect solution but maybe it might solve part of the problem? Tell me how it goes. :)