A heightfield / voxel engine like comanche
 

Remember the game 'comanche' for the PC? This guy has done a niftly little demo that lets you fly over the comanche data files. Just copy C1.DTA and D1.DTA over to it and run groucom.exe in dosbox.

Grab
http://advsys.net/ken/voxlap/groudraw.zip
From
http://advsys.net/ken/voxlap.htm

Source is included. There's a little bit of x86 ASM in there, but not too much. Would be a gas to port this to SDL and do a little comanche or scorched3d type game with it.

Cheers :)