Orks and Dwarves in a WWI setting? Sure. Here’s a set of fantasy WWI Rules.
rules
The Portable Wargame: Modern Rules
The Portable Wargame is a sort of mini-movement in the community: a series of user created rules for games based on checkers boards. They all look interesting and fun. Here are the rules for the modern version.
Cult of Ulric Warhammer Army
Cult of Ulric is a new Warhammer Fantasy fan-made army sourcebook. It’s very professionally done.
Hearts of Tin Horse and Musket Rules
Ross Macfarlane offers Hearts of Tin, a set of simple Horse and Musket rules:
Bushido New Dawn Rules
Bushido New Dawn is a set of free wargames rules for Japanese Fantasy/Myth skirmishes.