These are a few of the websites I used for research, and a few topics, chosen at random. (Actually, I used books to research Tangerine and Crusader, but it was the 1990s.) Thanks to Wikipedia for providing a free online encyclopedia to the world.
If you want a Muslim perspective on the Crusades, there’s a great article in The Atlantic Online titled “The Roots of Muslim Rage” (September 1990) by Bernard Lewis, but you have to pay (a lot) to access it.