The Crusades 1095-1291 offers a good overview of the First (and subsequent) Crusades)
The Internet Medieval Sourcebook has links to primary sources. Very clearly organized.
Gale History In Context will have a variety of popular and academic resources on the Third Crusade.
Salem Biographies will have biographries of major figures.
Britannica Online will cover all the major topics related to the Third Crusade.
First Crusade Only
The First Crusade and the Creation of Outremer has both primary and secondary sources. Hosted by Boise State University.