Yod.el (love the name!) is a Yahoo! Messenger client for Emacs.
http://marti.textdriven.com/yodel/
I tried it and it works well, but somehow doing IM in Emacs seems clunky. This may seem blasphemous to some, but perhaps some things are best not done in Emacs.
Hehe. I’ve actually been using jabber.el for my IM since I started working at Google. I’ve been holding off on Yod.el for fear that my productivity would be totally sapped, and also because “the right way” to do it would be to use a Yahoo plugin to a local jabber server.
Anyway, it is total blasphemy to suggest Emacs is not perfect for IM, and frankly, I find it great to have all the editing functions there without all that other IM goop.