Meebo has been one of the more known Instant Messagers (IM) out there because one of thing: no downloads necessary. This is a great boon for users with limited memory capacity on their hard drives.
Meebo is an instant messaging software that runs inside a Web browser, as AIM Express, which supports multiple IM services, including Yahoo! Messenger, Windows Live Messenger, AIM, ICQ, Jabber and Google Talk. Meebo makes instant messaging services more accessible to users who are unable or unwilling to download the software necessary to implement them.
So Meebo is the one for you if you think that downloading another program to your hard disk drive and still want to chat with your friends.