Bob Corderey offers Red Flags and Iron Crosses, a set of free wargames rules for playing World War II games in 20mm. The rules focus on small actions between Soviet and German forces.
Rules: WWII
MG-42 Two Hour Wargames Introduction
MG-42 is a set of free wargames rules designed as an introduction to Two Hour Wargames’ Reaction system.
Armour Battles WWII Rules
Armour Battles is a set of free wargames rules for playing out World War II tank battles. The author writes:
Armour Battles is an introductory set of World War Two wargame rules. Based on the larger Combat HQ rules, Armour Battles is a fully playable game.
Armour Battles features three armoured battles set in Lorraine, France in 1944 as Patton’s 3rd Army advances towards the Rhine. The first battle is a small meeting engagement between US and German tanks. The next battle has the Americans attacking the Germans. This is followed by the Americans attempting to break through the German positions as the Germans counter-attack with a Tiger I platoon.
Armour Battles includes all the rules needed to play these battles.
Note that you will need to surrender an email address for a mailing list to get the rules, but I think you could always unsubscribe later.
Warhammer World War 2
Warhammer has been adapted to every period I can think of. Here’s a version called Warhammer Panzer Battles