General

http://legacy.fordham.edu/halsall/sbook1k.asp

https://sourcebooks.fordham.edu/sbook1k.asp

Letters

http://www.shsu.edu/~his_ncp/Cruslet.html

A helpful bibliographic collection

https://cnu.libguides.com/c.php?g=23214&p=136617

Crusade and Art

http://crusaderimagery.com/lapina/

http://sscle.slu.edu/

De Re Militari

https://deremilitari.org/

That includes a motley collection of related sources

The Fordham Crusader States Project

A wealth of information