RMud
This is an exercise to learn Ruby. It was going to be Ruby on Rails, but Mongo is much more suitable to this task.
I intend it to be some sort of rudimentary extensible MUD loosely based on my great love, LPMud. Object scripting will be in Ruby, interacting directly with the MUD infrastructure, so content creators must be trustworthy, i.e. this is not the sort of game you open up to the whole world.