This a free game I enjoy to play around with every once a while. It's a soft body physics engine based mainly around transport/hydraulically operated trucks. It's basically a physics game come truck simulator. There are other vehicles too such as cars, off road vehicles, cranes, planes, boats etc. The game play is open ended, the maps you can drive on are essentially "sandboxes" for you to play on :). Also includes a WIP multiplayer.
A new version was released on Monday, 0.36 http://rigsofrods.blogspot.com/
Its very configurable to get the best out of your system but can bring even the most monstrous of PCs to their knees with every thing maxed out, and a few vehicles on the map at once :)
I recommend anyone who like such games to give it a try. There are of course bugs, but normally a hotfix patch shortly follows a major release to address outstanding issues. For me, currently there are no show stoppers.