ExtremeTech reports: "Tired of all the ads on AIM? Want access to more services than just Yahoo!? There are lots of IM client choices besides the big three—AIM, Yahoo! Messenger, and Windows Live Messenger (formerly MSN Messenger). The software we examine here lets you hook into any of these three services, and usually more besides, like Jabber. Not all of these applications will offer all of the features you'll find on the big guys—video and voice chat come to mind—but most of them do a good job of unobtrusively keeping you in contact with your comrades."
Many people have a problem of keeping up with all their friends and family on multiple IM networks (such as: AOL, Yahoo, MSN, etc.). This article gives you a review of several multi-network IM clients (such as: Adium, eBuddy, meebo, Meetro, Pidgin (formerly GAIM), and Trillian).
Some of these IM clients are web based so it doesn't require you to install any additional software.