I used ICQ in the mid 90s, up until about 2001 I guess. My fondest memory of ICQ is people getting all uppity over rumours and fake messages stating ICQ was going to start charging per message. I actually see people joining Facebook groups in 2009 about the same thing happening to that service, so I guess that sort of thing lives on today.
I started using AIM after I heard people talking about / I forgot my ICQ # / I forgot the name and ICQ # of most people I knew after an upgrade or reinstall. I honestly thought people moved on to MSN years ago, but people from the board said it was their chat tool of choice, so now I use that and MSN. By "use AIM and MSN", I mean I have both programs, I'll use AIM at specific times to join a chat (though I use it a bit more now just to randomly see if people I know from here are online) and MSN logs me in when I turn my Xbox on unless I remember to change my options. Almost everyone I talk to from my real life uses these programs very infrequently and I find it easier to message them on facebook.