One of my favorite pieces of terrain is the crashed meteorite, which is made from blueboard (my favorite material) and one of those green Styrofoam hemispheres used by florists. The hemisphere was gouged out with a knife, then coated with a couple of layers of glue to protect it and give some strength to the surface. A blueboard base was put on it and the 'ring' (also blueboard) was glued into place. Filler was used to alter the shape and cover any holes, then I finished the construction with a few Styrofoam 'boulders.' Painting was mostly a matter of blending to get a good 'glow,' offset by the darker mass of cooling rock. I have another one of these lying about, which is going to become a green, glowing meteorite like the "Loc Nar" ("I am the sum of all evil in the Universe.") from Heavy Metal. There's a scenario in that, most likely having to do with hordes of zombies or maybe a big mutant monster...
To the left is a close-up of a jungle tree. Slumped up against the trunk is a dead Ducal Militia, his body forgotten after some nameless conflict. The body is made from a GW plastic skeleton left over from the "Skeleton Army" box (you got about 30-40 Skeletons, several Skeleton Horsemen and a Skeleton Chariot for $20 - but don't get me started...). The head, gloves and lower legs of the plastic Militia were added onto this. The ragged clothing was made from paper towel, soaked in watered-down Elmer's. My Chasseur Sniper nearly shot this guy in one battle. Fighting Bauhaus, I got down to eyeball the Sniper's LOS and saw a pointy helmet under the tree. About to declare a shot at him, I suddenly realized the Militia were on the other side of the table...