@ Irrisor have you ever looked at bullet physics engine seems powerful , it's what blender uses, never personally messed with physics in blender before though just thought it might be useful http://www.continuousphysics.com/Bullet/
The problem is getting a Java wrapper around it, and even if we found people willing to do the work we'd probably rather spend our time on the Novodex engine instead since it's far superior to pretty much anything else out there.
50,000.00 is a chunk of change to find, if you want see how many people are stupid enough to buy your games 
Yes, I know bullet. It has more collision primitives (only dynamic trimesh is missing) than ODE. Though it has only basic solvers and joints. That's why people tend to use ODE for dynamics and bullet for collision detection. You can do both, using ODE with Bullet, and/or Bullet with ODE (see Bullet demos).
mcbeth said:
50,000.00 is a chunk of change to find, if you want see how many people are stupid enough to buy your games ;)
It's free if your game is also free. :P
darkfrog said:
It's free if your game is also free. :P
thats what I said.............in a not so direct way. :wink:
I won't claim that I have any significant experience with any of them, but I have at least fiddled around a bit with PhysX (Novodex), ODE, Newton and indirectly with Havok. Out of the four, PhysX has been the best, but also really expensive. Out of the free ones (ODE and Newton), Newton is by far the best in my opinion. In fact, Newton is very nice to work with.
<edit>
After a search in the Newton user forum, I found this post by "gaara":
Hey all. I've been working on a wrapper for Newton to work with Java. I don't know if there's already one out there, but I have made one for myself. It works with the current version (1.52) of Newton and uses LWJGL to render. Right now I have most of the functions done and a few of the more used callbacks working.
If this interests anyone, you can download the demo here. I have only tested on Java 1.5.
Newton and LWJGL are included in the zip. Run the two .bat files to run the demos.
niiiice. i've allways wanted a wrapper to newton…better get in contact with that guy 
If someone could make a Newton implementation connection via jME-Physics that would be awesome. The ability to easily switch back and forth between ODE and Newton would be an awesome way to validate differences between them as well.
The circle is nearly complete…
Matthew Jones and jjones7947 claim to have all of Newton wrapped, but I couldn't see that they offer it somewhere to the public.