A new Yahoo group is up for developing variants on Games Workshop’s Lord of the Rings system. They’re currently working on Star Wars, Gladiator, Samurai, Napoleonic and Pacific War versions.
Sgt. Perry’s Heroes offers a variant of the Legends of the Old West rules for miniature wargames set in the era of the Three Musketeers.
Games Workshop’s Lord of the Rings rules set has turned out to be very flexible, spawning several commercial sets, such as Legends of the Old West and Legends of the High Seas and innumerable fan variants. Legends of the Feudal Times is a set of feudal skirmish rules originally published in the French language magazine Vae Victis. The English translation is here.
The Lord of the Rings Rules variants Yahoo Group has a set for Napoleonics.