Algodoo

First things first, the start box is a good distance to the left of where the screen starts. I picked this spot because I thought it would make a nice thumbnail.

Second, this course is HARD. If you can complete it with your car, you have a great car and you can drive it well. Many obstacles are impossible without extremely good suspension and an uncanny knack for landing on your wheels. The car I used to test this with is an old Baja 1000 contest entry that has gone through hours and hours of the best tweaking and modification I could think of, and even so it can't go the whole way without perfect piloting and a bit of luck. The weight-sensitive obstacles are geared for 12-15kg cars, which is about what they'll come out to if you don't mess with density too much when you build it. Depending on the suspension, cars up to 125kg or perhaps more may work.

Third, I'm making a contest out of it. See it here:
Ultimate Offroad Challenge

Have Phun! Or have a great doo, should work for everyone. If it doesn't work in Phun, drop a comment.