Based on the Adventure in Prolog, over at the Amzi website, http://www.amzi.com/AdventureInProlog/, I started to work on a text adventure game for Drools. They are ideal as they can start off simple and build in complexity and size over time, I think as well they are a nice way to show of declarative relational programming. I know when I first went over the Nani Search text adventure game over at Amzi I thought, that's pretty nifty, true data driven applications.
You can find the latest source in github here, you'll need to be running HEAD or wait for 5.3:
You can get the latest HEAD binaries from hudson here:
You can view the 8 minute demonstration and introduction for the example here: