Ever since we got a 3D printer in the Geography Department at the University of Oregon, we've wanted to print out topographic models. Thingaverse user Markus Fussenegger (mfussi) has a nice compact Java program, Heightmap to STL, for converting height map images into STL files for 3D printing. Markus's program is available on Sourceforge through Thingaverse (http://www.thingiverse.com/thing:15276).
This is just a quick tutorial on how I got his code up and running on my Windows 7 machine...