I've mudded as recently as in the past year, and have done it in a very off and on fashion for the past five or so years.
I started on Aarchon, which is both serious and very funny. It's got a pretty nice lore, but it's also intentionally hilarious, and its gimmick is that almost all of its areas are stolen from pop culture. The newbie zone is Disney Land, and you slaughter various Disney characters, for example. There's also worlds of Final Fantasy, Starcraft, Warhammer, Simpsons, etc.
The other MUD I played I don't know if it could be strictly called a MUD, as I'm not sure of the specifics of what makes something a MUD, but it was a text-based MMO. One of the four "Iron Realms" MMOs, if anyone knows what those are. It REQUIRED roleplaying, which was actually a lot of fun, but it was super in-depth and VERY PvP. And, as I'm absolutely awful at PvP, and got a bit sick of the note-taking and macro-creating required to do well, I didn't last long.
Anywho, I'm a fan of both MUDs and MMOs. I am a fairly visual person, so I do prefer the latter, but MUDding was a great time, too. Though I don't know if I'll be back anytime soon.