Post any Yahoo Messenger website links in the comment section below.
As I quoted before on another post:
The server is easy to patch (its not fiddly and the dev made a patching program called Y!Patcher) and is pretty good if you want Yahoo.
It is unstable as hell though, Escargot does have Yahoo! support, but it only supports 5.0 - 5.5 and its a bit finicky to get working.