I have made a physics library called ArmaturePhysics. It is a set of python files that can be used together with Blender 2.49b to run physical simulations on Blender armatures. The main purpose is to aid in character animation. For example one can specify what forces are acting on a character (rigged by an armature), and ArmaturePhysics will
calculate the motion and rotation of the character. One can also use the library to simulate mechanical systems such as a bow shooting an arrow, or a tree shaking after the impact of some thrown object.
You can download the library, and view video tutorials, here:
The user interface is partially python, so you will need to edit some parameters in a python file. The python file is included in the Blender template files that are on the home page. There is also a graphical user interface, and some settings are made in the Blender 3D view. For example, if you name a bone “Force”-something, the bone will be interpreted as a force arrow. The direction and magnitude of the force is set by regular blender pose keying.
There is naturally a bit of a threshold to get started using this library, but once you have gotten the hang of it and set up your parameter file to your liking, running a simulation is just a click away (fingers crossed).
I hope you will find it useful!