This is a good one too - works fine WITHOUT helicopters. :-)
http://www.warehouse23.com/products/...pper-challenge
I've also run events in the Emporer's Garden - not an official product, so not sure if the mods will let it even be mentioned - can send you a copy.
Has rocks, trees and is on sand - not 'full blown' off road like Ozark (I really like that one, but it's a biggie, if you only have a few people - works good as a death race track too!).