For the World of Mystery project I revived the AC3D to jME converter. I might be the only one using this (non-free, but rather inexpensive) modeler.
The code is part of the worldofmystery: http://code.google.com/p/worldofmystery/source/browse/trunk/worldofmystery/src/de/wom/util/AC3DToJme.java