From War Times Journal, 1943 is a set of free wargames rules for battalion level combat in World War II.
Rules: WWII
Last Hussar’s World War II Rules
The Last Hussar blog has a set of free wargames rules for World War II. They’re a work in progress, so you’ll want to stop back by on a regular basis.
Big Battlesheet
Big Battlesheet is a set of free wargames rules for grand tactical 20th century combat. The rules fit on one page. A company is composed of 3 elements.
Big Battlesheet Direct Download Word File
WW2 Rules For Brigade Level Games
David Wareham offers a set of WW2 Rules For Brigade Level Games
Firefly Outgunned WWI Microarmor Rules
Firefly Outgunned is a set of free wargames rules for WWII microarmor. They’re based on the old Firefly and Challenger rules sets.