I hadn't seen this mentioned here before so I thought I'd post something about it. I use it in college where I'm behind a proxy. Obviously there is a security issue with giving out your passwords, but my IM identity really isn't worth stealing. Plus they do have a privacy statement, if you trust it
meebo.com is a website for instant messaging from absolutely anywhere. Whether you’re at home, on campus, at work, or traveling foreign lands, hop over to meebo.com on any computer to access all of your buddies (on AIM, Yahoo!, MSN, Google Talk, ICQ and Jabber) and chat with them, no downloads or installs required, for free!
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I smudged out my friends emails, not fair to be posting them