Is anyone still using Yahoo Chat?
I use it almost daily. It's called Yahoo! Messenger now and has a Windows desktop version (which automatically hooks into Yahoo! Mail and tells you if you have a new email faster than the web client does), a mobile version - though that's basically like text so I'm not sure what the point is - and a web client, which is what I use since I have a Mac.
If you have a Mac, you owe it to yourself to use Adium which is a lightweight client that bundles all messenger services into one package. In this day and age, It doesn't make much sense to have seperate programs running when you use multiple services.