"MUDs (Multi-User Dungeons) are text-driven cooperative or
competitive games that you can play either straight from your
terminal using the Telnet protocol or through a separate
application specially designed to play MUDs. The majority of MUDs
are free to play. Here's how you can get started with them.
"To find a MUD that appeals to you, visit a MUD-list such as The
Mud Connector or Mud Magic. Both have reviews and top-rated and
'game of the month' features to help you find a MUD to jump into. I
recommend Mud Magic for beginners, as it is easier to navigate and
provides clear, comprehensive lists of top-10 MUDs..."