What On-line, for download or for purchase software-based games provide fun language practice for learners of Chinese? What level of learner are they best suited for? What platform do they run on?
One game I suggest you check out is Enter Zon - an MMORPG specifically for learning Mandarin.
Essentially you run around in a game environment and have all sorts of dialogues about different things, with the end goal of improving your Mandarin. It's pretty neat.