Villehardouin is a free map-and-counter board game from the great designers at Perfect Captain. It’s a game about the Byzantine Reconquest of the Morea in southern Greece in the year 1263 AD.
Battle of Red Gate is a Crusades scenario featuring the Franks and Damascenes in 1106.
The Shadowed Realm site has an article on Richard the Lionheart and Saladin, which provides good background for anyone thinking of starting a Crusades gaming project.
The Krigsspll.dk site offers a very large selection of downloadable flags for the Crusades. They are all very well done.
The Fanaticus Site has a set of Crusader banners for you to download and print. They’re in 15mm scale.