I've used all of the above. I actually started back with America Online Chat (when it used to cost money per the minute!) Then found AIM, Yahoo Messenger, ICQ, but MSN was probably my favorite. It was the one that had most of my friends on it-- friends from my forum community.
We'd chat about the role playing games we were in, and about life in general. I always threatened that we'd do a meetup someday, and I'd bake a chocolate cake. 😊
I used both the Windows and the Linux variety of applications as well, although, I really don't remember what the name of the multi-chat software I found was that I used for Linux, I do remember that it had a strange quirk where it would mix up communication chats, which lead to some confusion!