The Crusades also opened a world unknown to most crusaders to that point. In many ways, the Middle East at that time was more developed than Europe. Medicine and architecture, for instance, were well ahead of those of their European counterparts.
For example, in early Norman times, fortifications used angled rather than circular surfaces. Corners were much weaker than curved surfaces, and square towers could be taken in a number of ways. Corners could be breached, or towers could be weakened to the point of failure by digging underneath the corner.
Circular structures, however, were much stronger to direct attacks, and could not be weakened significantly simply by digging. This circular building technology was already in place in the Middle East at the time of the Crusades, and was brought back to England with the Crusaders. We can see evidence of this today in England, when we look at building dates of the many Norman castles still standing.
In medicine, medieval doctors in the Middle East based their practices on the ancient Greek texts that were available to them, whereas in medieval Europe, medicine was dominated by the tenets of the church. Middle Eastern doctors performed surgeries, used a variety of drugs for treatments and also encouraged and supported the education of women as physicians. As with architecture, the ideas encountered in the Middle East eventually made their way back to Europe with the returning Crusaders. Having witnessed "real" medicine in action, it is very likely that the Crusaders beliefs in the all powerful church were weakened as a result.