In my copious free time, I do some work on a mud named DarkRifts. The mud itself runs on MudOS on top of a mudlib based on a mudlib based on TMI-2. I've worked on a few other mud projects, but decided I didn't want to run my own mud since I don't have enough time for that and it'd be better to help out with someone else's mud.
The mud is still pretty infantile in terms of maturity of the codebase and player base. We have seven guilds that are in-game (two of which are "starter" guilds) in two realms with twenty-nine different areas and several cities. We've got a few alpha-testers who come irregularly.
There's a lot of polish work to be done--but we're not at that stage yet, though we are progressing. One difficulty is that our alpha-testers are pretty irregular in their testing. So the mud is pretty quiet most of the time (I think we average 2 players online). The other difficulty is that we could use a few more coders to help even out the rough edges on that side of the equation.
Anyhow, if you have any interest in seeing what we've got going on, helping out, or otherwise chiming in, check out the DarkRifts website and/or add a comment below. If you log in, my name is "Flake". I idle there during the day and do some work on nights and weekends (I'm in Boston, MA which is Eastern Standard Time). Please drop in and say hi!