Away from your computer? Friend doesn't want you to download MSN Messenger or AIM? Head over to eMessenger. It allows you to use MSN messenger, AOL Instant Messenger or Yahoo! Messenger via your web browser of choice. Well, I've tested it with Internet Explorer and Firefox 1.5RC1.
It works pretty well most of the time, and I make use of it a few times a week usually.
Edit: I should also mention MSN Web Messenger. It finally works in Firefox, so I guess I can support it. Check that out too. Only works for MSN Messenger though.
This Post