The "Burning Man" festival would be a great way to finish off your trip, but since it doesn't start until August 29th, you'll probably be back in France by the time it starts.
The event is part performance art and part Pagan celebration, but mostly it defies description. It takes place a little North of Reno, which is just across the California/Nevada border near Lake Tahoe.
For more details, check out
www.burningman.com
ScottMate