Abydos
Made from scratch in Delphi, screenshots are available on the homepage. Medieval based, newbie friendly.
Alternate Universe MUD
Alternate Universe is a free online multiplayer game, inspired by science-fiction, and entirely custom-written in Java. Includes codewars extension.
Angalon
A medieval theme. Features sections on theme, players, beginner's guide, message board and immortals.
Banished Lands
A custom code base mud with multiclassing, color, and clans.
Banished Lands
Sections on online help, players, areas, rules and policy, clans and brethren.
British Legends
A port of the Compuserve incarnation of the original Multi-User Dungeon, written by Richard Bartle and Roy Trubshaw. Offers detailed assistance to new players, FAQs and a brief history.
Dawn of the Ages
A player kill MUD. Written in Java for a new, stable codebase.
DestinyForge
Gaming Engine running Realtime and Turn based Fantasy Wargames.
Forest Edge Building Manual
Information on building rooms, mobiles, objects, shops and pets.
LegendMUD
Features a variety of historical contexts, including ancient Ireland, Homer, Queen Elizabeth, Dante's Inferno, goldrush Melbourne, and Kipling's India. Supports a variety of styles of play.
Materia Magica
Features forums, online status indicators, and references.
MUDII
MUD2 is the latest incarnation of the very first MUD (Essex MUD/MUD1/British Legends.)
SocketMud
Bareboned MUD codebase written in C, and is available for download.
Symelion
Science fiction roleplaying via web-based chatrooms.
The Land of Drogon
A multi-user reality in the style of a traditional adventure like Zork or Colossal Cave.
UrMud
Set in ancient history featuring a self-growing ecology, advanced combat system, houses and clans.
Ursha Null 7
A science fiction mud. Features sections on game play and technical information.