LambdaMOO is mostly people being idle. There is, however, a spiritual successor called ChatMUD. It's based on a fork of a fork of the original LambdaMOO server called ToastStunt (forked from Stunt). It seems to have a bit more pep in its step if you're looking for a semi-active social / programming MOO.
played a huge part in my programming evolution, too. learned OO from programming in it, and then learned C from hacking on the server and various offshoots of it