Since I have now transitioned from C to C++, there are a few more options for libraries that can be used. One of them is the Bullet physics library, which seems to be nicer than ODE (which I am still having some trouble getting along with).
Bullet seems to have a clean API, and it seems to be actively developed. Also, the support for various hardware seems interesting (e.g. the PS3 SPU support). Perhaps OpenCL will be supported too once it is released?