I am a fan of
Hirst Arts molds. By buying a few of their molds and a box of plaster of paris you can turn out some really slick looking terrain in a short amount of time. The molds have a pretty high cost up front but once you have made a few pieces of terrain your overall investment really works out.
One of my more recent pieces of terrain that I made was a bunker. This piece of terrain was super easy to make. I just made a bunch of casts of the Fieldstone Mold (#70) and used a door from the Starship Mold (#301). For the top I cut out a piece of plasticard the right size and it just fits on the top so you can open and close the model. I then glued the completed model to a piece of hard board and painted it up with my terrain paint (Applebarrel Paint.)
It looks pretty good and we use it every so often in a game. We don't really like the whole 'embarking and disembarking' out of buildings so we just use it as a piece of 3+ cover.
