CIS
I had a Compuserve account in the 1980s and early 90s, but just to access a couple of company forums. I frequented a couple of Silly Con Valley BBSes starting in the 300bps days, but mostly used Delphi and/or BIX (starting with the BYTEnet beta) when they came online ... at least when my home Internet connection was down for whatever reason(0). I never really liked CIS. Nonetheless, RIP CIS Forums. You helped a lot of people along the way.
(0) Hey, we were still mostly doing the NCP thing thru' '82, what were you expecting? Perfection?