I am a big fan of physics-based games. I have used Phys2D for a while integrated with a home-grown 2D engine.
Over the last 2 years, I have looked over JBox2D, JOODE and various other physics engines/resources out there. I decided I wanted a more concise API and a smaller library size. So, I have recently put together my own physics engine I call simpull.
I would like you to check it out and comment on what you think. It is most certainly not a kitchen sink of all the physics goodies you could want, but it does have some important and extensible features.
I am quite interested to know what you think about performance.
Be gentle and take a look:http://code.google.com/p/simpull/
Additionally, I have also started another open-source project to extend PulpCore (a quite impressive project you probably know of) to integrate simpull physics. Its called Simpull to the Core and a demo is at http://simpull2core.sourceforge.net/