Personal Things To Bring:

 If it's not on this list, consider leaving it at (babylonian) home. If in doubt, leave it out.
If you bring it in, you have to bring it out (or give it away).
(The following list concerns traveling a long way to a gathering. Much of it is overkill for a weekend trip. Items in each section are listed in approximate order of priority. Items deemed essential are marked with "*". It's all just the opinions of a few persons, in any case.)
A tent, backpack with extra straps,  sleeping bag,  pad/mattress (for sleeping on), sheet/blanket,  tarp, bunji cords,  hammock

 hat,  portable jacket with hood,  good broken-in walking shoes/boots,  long pants/skirt,  bandana,  socks and underwear,  shorts,  sweater,  long and short sleeved shirts,  raingear,  a second pair of shoes/footwear for swimming, towel, traveling back clothes (You need less clothing than in Babylon.Bring clothes that protect against sun, insects, cold and rain but avoid over packing.)

large plastic bowl with a hole in it for a string or clip, cup with ear, fork and spoons with holes, water container (wineskin), flashlight, (Swiss army) knife, lighter/matches, plastic bags, string, extra batteries, camera (always ask before taking someone's picture), film

 this sheet, road and gathering maps, keys, uniquely colored messaging paper, method for identifying vehicle from a distance (ribbons), signs/flags (for marking campsite), ID/drivers license, timepiece and tickets if needed for travel

toothbrush, organic soap/shampoo/toothpaste (Dr. Bronner's), sun block, toilet paper (one roll with coffee canister to put it in), Skin So Soft or other organic insect repellant, first aid cream/spray, bandages, moleskin, Tylenol/Aspirin, needed medications, dental floss, birth control, calamine loti on, water purifying method, calling cards

Green energy:
Canadian/US currency, credit cards (You won't need any money once you get to the gathering, except for donations to the magic hat)

Lots of it!

crystal, portable musical instruments, pen, paper, star finder, things to give/trade (Welcome Home! stickers)

Snack/Sharing Food:
 (delicious and nutritious vegetarian meals are served) dried fruit, peanut butter, nuts/trail mix, favored sauces (BBQ, peanut), spices (no oregano) The Rainbow, shit happens. Go with it. Everything you need will come to you. Welcome Home!>