The jMonkey Engine framework (jME) is a high-performance, 3D scenegraph based graphics API, written in Java. It supports both LWJGL and JOGL OpenGL rendering systems. jME is completely open-source under the BSD license and you are free to use it in anyway you see fit, be it hobby or commercial. The current version is jME2, jME3 is in development.
Please read the contributors handbook and feel free to add any details you think might help prospective contributors such as yourself.
Also consider participating in Google Summer of Code 2010!
"UnsatisfiedLinkError: no lwjgl in java.library.path" solution
Video: Creating Games on the Java Platform with the jMonkeyEngine (JavaOne 2008)
See also: Free 2D/3D models