Quite some time ago there was a Crusades Rule set by Dr Brendan Moyles called Shattered Lances. It proved popular and there was a supporting website. Lots of good things about Shattered Lances in terms of real period flavour. It was particularly good on the Ghulam wave attack. The website is now gone but the rules are still available from Outpost Wargames Services.
I also very much enjoyed Ager Sanguinis by James Roache, again lots of flavour and some good mechanisms. Ager Sanguinis is a Piquet influenced game. I've had some great games with it. James's plans for a second edition are currently on hold.
Currently I'm very interested in adapting Never Mind The Billhooks into a Crusades rule set. So much so that I'm having a trial run this week. The post on my blog was really to ensure the essentials of battle in Outremer stuck in my mind. I hoped it might prove interesting to others too. If my test game proves successful I'll write it up on my blog with a link here. So far, it's looking promising.
Yes, I saw the Lion Rampant Crusades book is now available. I'm hoping someone will review it.