Wolsung is a set of free wargames rules for steampunk skirmishes. The company also sells a variety of figures to go with the rules.
James Clay has written a fine article on wargaming in the world of the Difference Engine.
For those who don’t know, The Difference Engine is a novel by William Gibson and Bruce Sterling that takes the reader to a Victorian world in which Charles Babbage’s Difference Engine drives cybernetic steam engines. While I did not enjoy it as much as Gibson’s Neuromancer, it still was a good read.