It's a good idea to suggest that the participants use a CVS-system to keep control of their files:

From Wikipedia: Revision control (also known as version control (system) (VCS), source control or (source) code management (SCM)) is the management of multiple revisions of the same unit of information. It is most commonly used in engineering and software development to manage ongoing development of digital documents like application source code, art resources such as blueprints or electronic models, and other projects that may be worked on by a team of people.

Every year we have had a discussions of whether to put up a special server to be used for source control. For practical purposes, we always end up not doing this. There are primarily two reasons for this:

It is a lot of work and we wouldn't really want to bother with a failing server in the middle of it all. There are very good free online as there are very good, online free services, such as Assembla (http://www.assembla.com/ )

It is really important to encourage the participants to use a version control system, as it can help them cooperate and work faster. It will save them a lot of work, and a lot of confusion, as they won't have the usual confusion of 'who has the master version' of some file.

Experience from NGJ:

Have you:
Found a CVS-solution for the jam?
Have you tested that it functions according to your needs?
Have you informed the participants about the CVS-system before the jam, so that they can prepare themselves for working with it?