Two Python scripts for Blender here that may be of interest.

Drop To Ground
This Python script for Blender 2.31-2.32 is useful for making objects in a scene rest on a ground mesh. To use it, you name your ground mesh "Ground", select the items you wish to drop onto it, put your cursor over the script window and hit alt-P. Note that your ground mesh must not be scaled or rotated, so if you have done so, be sure to press Ctrl-A to apply scaling and rotations before using the script.

Drop2Ground.blend Sample .blend file with script embedded

Follow Terrain
This Python script for Blender 2.31-2.32 is a branch of the Drop to Ground script. It allows you to link the script to a Blender object via a Redraw object script link, which then lets you move the object in realtime while it stays glued to the surface of your ground mesh. It works for animation, as well as when linking objects to paths. The same rules for the ground object apply as for Drop to Ground.

FollowTerrain.blend Sample .blend file with script embedded
FollowTerrainPath.blend Version that allows Path-parented objects