The Napnuts site has a set of rules for conducting a Napoleonic Peninsular campaign. The Peninsular Campaign makes for a good campaign because of its relatively limited scope.
Basement Generals has a general miniature wargaming site with an extensive victorian science fiction section featuring battle reports of their Master of the World Campaign, plus photos of their figures and models.
Clauswitz’ War: Theatre-Level Napoleonic Campaign Rules is a set of free wargames rules for Napoleonic campaigns. The author writes:
These rules are designed to be used to represent theatre-level campaigning with armies of several corps per side during the Napoleonic period. Each turn is a day, and maps covering an area from 100 – 500 miles on a side with good detail (roads, rivers, towns) should be used. The intent of these rules is not to depict campaigning 100% accurately, but to provide a referee with basic guidelines for running a Kriegspiel-type game for the generation of tabletop engagements. All dice are ordinary 6-sided dice.
Gold, Swashbucklers and Pirates is a set of free rules for creating a small wargames campaign using gangs.
For those of you looking for a different setting (indeed, a different world) for your steampunk games, you could take a look at Steamworld Daleth. The author writes:
Steamworld Daleth is a gothic world on an alien planet. Call it an imaginary country, a geofiction or a follie. During the many years I have worked on Daleth (now over 20 years) the world has become what she is now: a steampunk/gothic world where the echo of the Victorian Age still sounds, but where many odd things are yet to be discovered. It’s a mix of fantasy and reality, a dreamscape of my imagination. Daleth can be used as a setting for the role playing game Intrigue & Illusions, but is not developed as such. Daleth is much more than a mere setting for a RPG. It’s a world with its own dynamics.