The next project is a steampunk tunnelling machine, a mechanical mole. It's part of a group build: Nine modellers each have a foot-square tile with basic groundwork; the assignment is to build a steampunk war machine (Jules Verne-style). Some of the tiles are Prussians, some are French; there are a few simple rules about the scale, which way your machine should be facing, which way the river is flowing, etc, and we've made a group purchase of a whole mess of teensy Prussian and French soldier figures.
At the local sci-fi model contest in September, everybody brings their completed tile, we set them all together in a grid, and voila! Awesomeness happens!
So far we've got a giant robot, a mobile fortress, two airships, a land ironclad, a railgun, and a mechanical mole. (A couple of the guys are still thinking about what to build.)