The UK Battlefields Trust has an extremely interesting site with information, maps, ground and air photos of English battlefields from the Celtic and Roman periods through the Stuart uprisings.
Battle of the Five Armies Scenario
Merlin Larson has a well researched scenario for wargaming the Battle of the Five Armies from The Hobbit.
My Kingdom For Horse Free Medieval Rules
Ian Hopping offers My Kingdom For A Horse, a set of free wargames skirmish rules for the dark ages and medieval periods.
John Bull and Patriots 2nd Edition
The Perfect Captain offers the second edition of John Bull / Patriots, their rules set for game of the American Revolution and War of 1812. These are the most visually striking rules sets available today — either commercially or free. And these are FREE!