The Trash Tokyo rules from WilsonClan is designed to be a miniatures wargame for people not into miniatures wargames. I have a collection of Godzilla toys, and think I may try these out.
rules
Indian War Rules
Fred Diamond has a simple set of free wargames rules for playing the Indian Wars in the America of the late 19th century.
Fallout Miniatures Rules
Fallout is a legendary computer role playing game. Set in a post nuclear world, it has a 1950s science fiction aura. Here’s a miniatures game set in that world.
Aeronef Logs
Similar in spirit to the late, lamented Space:1889 cloudships rules, Aeronef is about Victorian era armored flying gunships. There are some outstanding ships’ logs for the game here.
Blood Bowl Soccer
Blood Bowl is one of Games Workshop’s smaller games, but its been around for as long as I can remember. Here’s a Bloodbowl variant that uses the game to play European "Football" — soccer.