The C++ side of the MUD engine that I was working on is fairly complete, aside from some refinement that's bound to happen as I try to build something on top of it. It's nice to have a solid base for that now, though.
As for what to build, I've got a few ideas floating around for that, but it's taking some time to get that worked out. I'm thinking about splitting discussion of that off to a separate LJ account, so that those that are interested can keep up, while those that aren't don't have to be burdened with scrolling through it. I'd like to use the name of whatever I do create for the account, though, so probably best to come up with that now... I could use the name "Sanctuary" that I was kicking around when I was playing with ideas in college, but I don't really want to be confused with this :-)
I'm still kicking around theme ideas as well, but leaning toward medieval fantasy... for one, it lets me pack more of the stuff I'd be interested in implementing as far as gameplay goes.