Carsim is a little "demo" I wrote to experiment with Verlet integration. When I have time I'll write a bit more about how I went about it, and what the good/bad things are about the scheme and my implementation. In any case you can download the windows executable, the source, the MSVC 6.0 project file and a makefile (for linux etc) using this link:
All I'll say is that it is quite slow (partly because I just put it together as an experiment with the method, and partly because I think the whole scheme is naturally slow), and some aspects are incomplete - e.g. sometimes objects get locked in penetration. Also, I've concentrated on the rigid-body aspect - the car handling and car AI are very dodgy!
Some (ugly ;o) screenshots:
Stacking. The 5 boxes stacked up stay stable for quite a long time, until the very small amount of jitter/drift makes them topple over:
General interactions - here a car has crashed into the stack above: