When I was in highschool, and I had limited play-time on my parent's computer, I would log onto a MUD called "Legends of Terris". It was based out of (Great Britain? England? What was the difference at the time?)
Anyway, I was introduced to it by my then-boyfriend/now-husband and was the first social game I ever played via internet. It was easy to begin, difficult to master, and was a helluva lotta fun.
And yes, it still exists today: Legends of Terris
My characters still exist, it can be FTP or paid premium. However, the player base (last time I logged in) was tiny, so I never really got back into it like I used to...