Meebo – A free Multi-Service IM Client
Meebo lets you access your friends on all the major services (like Yahoo, MSN, Goggle Talk, ICQ, and Jabber) in a single buddylist, from your browser. Also you can sign-in to all this services separately. No installation is needed.
The best thing about this service is, you can chat across all networks, using your already existing IM account or by creating a free meebo login. It also allows you to play games, video conferencing, file transfer, etc. it also provides shiny rocket launcher in meebo IM window with that you can launch any application with your friends.
I am using this service from last two years, just because I am able to add my all friends from yahoo and gtalk in single list and able to chat with them from anywhere, just using browser. It’s really working very well.