I had AIM, ICQ, and a few others. Pidgin (originally GAIM) let you send and receive on all the services from one app, which was very handy.
AIM and ICQ were the big ones back in the day, nothing ever was as big as that.
ICQ was released 1996; Pidgin (as GAIM) was November 1998; Jabber was released in 1999. Those were good times.