imo.im is one of the most impressive less known web application. Its a free tool that allows one to use MSN, AIM, Yahoo, Gtalk, Facebook, myspace and 'Skype' to keep touch with their buddies no matter which OS or desktop is running the browser. Hence alleviating the issue of installing different desktop clients or having multiple windows/tabs for each chat client.
The Linux users who wanted to always use gtalk will surely be happy by this imo feature. The designers claim that one can voice and video chat no matter which OS you use.
Unlike Meebo, imo uses a very simple, intuitive and easy to use GUI. The friends list is neatly grouped and aesthetically displayed. Apart from this the designers have added value to the application by the 'Broadcasting', image sharing and 'white board' features.
All in all its a pretty good application that deserves 4 out of 5 stars and is worth a try.