Back in the dark (pun intended!) days before Cheetah 3D added lightmapping support, perhaps the best lightmapping tool for indie game developers was a program written in BlitzBasic or Blitz3D (not sure which) called gile[s]. (I don’t know about the [s] bit, but I guess it looks cool or something.) If you don’t know what lightmapping is, or you’re past that now (most modern console games have real-time shadows) then you won’t care, but if you’re interested, you can get gile[s] here.
Meanwhile, the developer of gile[s] has been working on a rather impressive little game called Youropa, which appears to be built around gravity and other physics fun. Worth a look when it comes out, I think. If nothing else, it’s beautiful. More Youropa screen shots and videos here.