-----I HAVE NOT CREATED THIS LIBRARY, I HAVE ONLY COMPILED IT FOR PSP-----
Original version of this library is here
It's the library LiquidFun compiled for PSP. It's based on Box2D 2.3.0 but it expands its functions supporting particles and softbody simulations. You can create multiple particles system with different density, velocity, viscosity ecc. Particles simulutaion is a really heavy task for PSP but it works. I used this library for creating the example app.