The MUSH (Multi-User Shared Hallucination) branch of the MUD family tree includes games that tend to be centered around roleplaying, world-building, or socializing, rather the combat and level-gaining aspects of other types of MUDs.
The MUSH family includes TinyMUSH, PennMUSH, and TinyMUX as well as other less common relatives.
A game to own, train, race, and breed, a stable of horses. Not an email or message board SIM stable, but in real time with the help of tinymush 2.2.5 www.horseworldmush.com
Original themed MUX set on a group of forgotten tropical islands, inhabited by the descendants of circus clowns, acrobats, carnies, side-show freaks, and visitors from other times and realms. carnipelago.wolfpaw.net
Based on the roleplaying game of the same name by Holistic Design. A delightful combination of space opera and medieval fantasy, the Fading Suns Mush provides a rich setting for political and economic conflict. fadingsuns.org
Buffy the Vampire Slayer MUX is a roleplaying game set in the world based upon the two hit television series by creator Joss Whedon, 'Buffy the Vampire Slayer' and 'Angel'. buffymux.betterbox.net
Atlantis is an online roleplaying game centered around faction-based submarine warfare. It is a combination of science fiction and fantasy. www.hawkgames.com/atlantis
Although the game itself is now defunct, this site describes the MUSH world of Poddington-on-Slossip, a small village in Cornwall which, strangely, does not appear in any of Baedeker's guides. www.grandiose.com/poddington
Fort Bloodshed is set in the Wild West, as portrayed in classic Western movies and popular fiction, in which characters can create their own legends. www.bloodshed.org
Online gaming environment using Hero System 5th Edition rules. Unique, detailed game world. Interactive storylines and plots. www.angelfire.com/games4/oim