Having wondered what goes on behind the scenes of a rally and how one can help make it happen, I want to put this info where it can be referenced by any one else who wants to get involved.
Tim.Find the website of your favorite and/or closest rally, and look at the contact list. Call or email the chairman, rallymaster, etc and find out when the next organizer meeting is & where. Attend the meeting to meet the organizers and just listen to how much there is to do. Offer to shadow one of the "chiefs" to see what the position involves. Or, if they need some smaller details taken care of, raise your hand.
Then, get on the email list for future communication. As rally weekend gets closer, there will be more to do, and it's almost guaranteed that your help will be much appreciated.