Certainly do! Some of the oldest and most creative of the MUDs are still in operation, and still being continually updated. One still-running DIKUmud that is still in operation and is absolutely amazing in regards to the ~25 years of constant evolution is Duris Mud. If you have any interest in MUDs or MUD programming its definitely worth checking out.

http://www.durismud.com/ or telnet to mud.durismud.com 7777