Let them edit it throughout the semester, and then only give access to that site (hosted on a machine on a LAN, not connected to the internet). Then everyone would have the same information base, and they could search for information. You could even keep the information alive through semesters. Make sure it's read only during the test. And you can go through it quickly after writing the test to make sure no information is too helpful.
Even better, or also, you could host a stack exchange like service too, that people can record and exchange information for the projects they do during the semester. Teaching is the best way to learn, after all...