jMonkeyEngine.org

Are there any games that are open source on JME3? I feel like it would be a great help to me to learn JME if I could play around with a finished product and see how they implement and use some things instead of trying to feel my way through it with the help of the tutorials.

http://code.google.com/p/rise-of-mutants/

But it’s still in development. But you can learn about entity system and different stuff.