Also see http://www.monoposto.co.uk/about-mrc/f- ... ng-racing/
Thinking out loud
A tent (unless you prefer hotels, pfffff)
Living/cooking/clothing stuff for tent
The race car!
Enough fuel (plus a little spare just in case)
Race licence (and upgrade form if you want signatures)
Helmet, race suit, gloves, boots etc
An awning - one of the Easy-Ups, a sheet of tarpaulin, a sturdy awning or a truck with an awning...
Some jacks that can lift the car - ideally both ends at the same time, but one end at a time will suffice
Wheel nut tool and torque wrench for putting them back on
Misc washers, nuts, bolts, rivets, split pins
As many spares for your car that you can fit in your vehicle - leads, plugs, coils, suspension, rainlights, rodends, brake lines.......
Handcleaning wipes or Swarfega-esque stuff.
Tyre pressure gauge
Tyre pressure inflator (either a camping style 12V one, or a compressor etc)
A Towel (and some peanuts and beer, just in case the Vogons arrive)
Cables for electric hook-up if you're lucky
A change of underwear
A laptop (if your car has fancy computery bits)
Helpers - the more the merrier, ideally aged between 12 and 60
A sense of humour
Not too much expectation
If you have a "pitcrew"
Pitboard and numbers
You will forget to bring things you will later need. You will bring lots of stuff you will never ever need, even though it seems so likely that you daren't leave them at home. You will bring more and more stuff to each subsequent race. It's really a case of trying to bring EVERYTHING YOU HAVE, and only not bring stuff if you can justify not needing it.