Lancer Runolfsson offers Six Page Napoleonics, a set of simple Napoleonics rules for a game in four to five hours.
Elan Deluxe is a set of free rules for playing Napoleonic wargames. Once published professionally, it now is available online. This is a very well done, and interesting set of rules. The nominal scale is 1-50, with units representing battalions and regiments.
From Baccus miniatures, Old Trousers 6mm is a set of quick-play Napoleonics, played on a 2 foot x 2 foot board.