Here's a little level generator I made this morning in about 5-6 hours. It uses premade rooms and can go through 15000 iterations in about 10 seconds. It picks randomly from some premade rooms then attaches them by "doors". Development was done live on twitch at http://twitch.tv/encryptedcow
I may make a tutorial for this in the future, however the code is very messy at the moment.
Edit: I felt like doing a multiplayer versiona s well because why not https://dl.dropboxusercontent.com/u/71526571/levelgenmp/index.html