Strange Aeons is a skirmish wargame of Lovecraftian horror. You can get a Strange Aeons demo kit here, and the quick reference sheet for the second edition Strange Aeons here.
Miniatures Rules
Newcastle Quite Decent Ancient Skirmish Rules
The Newcastle Quite Decent Ancient Skirmish Rules are a playable summary of a much larger set.
Warhammer 40K Battle Primer
Games Workshop offers a free pdf of its Warhammer 40K battle primer, which contains basic for moving, shooting, fighting, using psychic powers and morale, along with other material to get you started.
Inquiry, Inc. Mystery Rules
Inquiry, Inc. is a set of free rules for playing games with Hasslefree’s not-Scooby figures.
Tom’s Ancient Warfare Rules
Tom’s Ancient Warfare Rules is a set of free wargames rules for the ancient period.