Land of the Lead has a set of one-page Napoleonics Rules. They’re designed for play with a “reinforced division” per side. Scroll down to the bottom of the page to find them.
Blaster Simple Science Fiction RPG
From the author:
Blaster is a generic SciFi RPG in the 26th century where mankind’s unity has been sundered by war and where a few good men can still make a difference.
More like Firefly and Buck Rogers (the 1930′s version) than Star Trek you will form a team of adventurers who have a small starship which they can use to explore, travel, trade and fight against the dying of the light.
As usual both the core rules and the setting are single page affairs and are completely compatible with other titles in the Dead Simple RPG series.
FUBAR One Page Modern / Science Fiction Rules
Fubar is a good looking one page set of modern and science fiction rules.
Age of Fantasy v 2.3
The folk at One Page Rules have released version 2.3 of their Age of Fantasy Generic Rules. The rules have one page (front and back), and there is a vast list of army and faction stats to download as well.
Spartacus Gladiator Rules
Andy Watkins has one page set of rules for games involving Roman gladiators. You can use the fine Wargames Foundry 28mm Gladiators to fill your arena.