Copied from Beermountain.com. Take some of this with a pinch of salt.
The basics - your personal survival kit
Passport
Cash (in Euros)
Credit card (no good at French self service stations)
Tickets
Driving licence
Photocopies of passport/licence
ACO ticket holder (BM model or similar)
EU health card (replaced E111 in 2006)
Wash kit
Ear plugs 9foam or wax type)
First aid kit (inc plasters, immodium, neurofen, alka selzer)
I Pod with play lists
Favourite CD’s (if no I Pod)
DVD's (if you have a DVD player)
Airbed & airbed repair kit (spare plug a must)
Pillow
Small radio & earphones (tune to 91.2 FM)
Ear defenders (you can use on top of earphones at track)
Sleeping bag
Torch (compact LED model)
Sun cream (SPF 25 or higher)
Towel
Mobile phone & charger
Camera & charger/spare battery
DV camera & charger/spare battery
Overnight bag (for ferry)
Wet weather gear
Team shirt
Clothes
Trainers
Flip flops
Warm jacket/fleece
Sun hat
Golf umbrella (sun and rain)
Book (there may be a quiet moment)
Pen
Sunglasses
Batteries & spare batteries
For your car
European breakdown cover
Copy of insurance documents
Headlight beam converters
BM stickers
Maps/directions
Satellite navigation
Power inverter (for charging cameras etc)
Team equipment - for your team members to bring
Tents
Gazebo
Spare guy ropes
Mallet
Spare mallet
Cable ties
Gaffer tape
Electrical tape
Super glue
Jubilee clips
Tool kit - screwdriver, pliers, hacksaw, hammer
Tent pegs (including some rock tent pegs)
Mesh fence (x50m)
Fence picket posts
Airbed pump (12v electric from car)
Hose pipe x 50m & hozelock adapter with screw thread
Hose pipe splitter (to share connection with others)
Spare hose (50m)
Main table
Side table (for BBQ preparation)
Chairs (folding type an advantage)
BBQ
BBQ tools
BBQ fuel
Propane for gas BBQ
Matches or Zippo type lighter
Rubber gloves (x2 pairs)
Cleaning materials
Cool boxes
Flagpole
Flags
c**ktail accessories & ingredients
Corkscrew & bottle opener
Saucepans (old)
Frying pan (large & old)
Chef's knives
Spices
Plastic glasses
Disposable plates, knives, forks, spoons
Food for first day (frozen curry/chilli con carne ideal)
Water (5-8 litre bottles)
Kitchen roll
Wet wipes
Nutrodol (for inside toilet/shower room)
Doing it in style - for the camper who has nearly everything
Generator (ideally over 5kw and near silent)
Electric kettle
Filter coffee machine & filter coffee
Extension flex with plug/socket for generator
RCD safety trip box
Jerry cans and fuel for generator
Christmas lights
Beer fridge
Food fridge
Plastic dustbin
Chemical toilet and tent
Broom
Walkie talkies
Classic board games/poker
Water pistols/cannons
Television
DVD player
Washing line & pegs
Bikes
Cool box with bacon etc from UK
Electrical cable (x100m)
French socket adapters
Stores tent
Solar shower
Toaster and long life bread (if this is your thing!)
Making a show of it - serious equipment for the LM professional
Bar
Disco lights
PA system
Mirror ball
Smoke machine
Bubble machine
Ice maker
Satellite television kit
Compass (for satellite set up)
Pit lane scooters
Scaffolding for track viewing platform
What to leave behind
Laser speed trap detector (illegal in France)
Fireworks (you can buy in Le Mans)
LPG (in large quantity, varies by ferry operator)