This is generally categorized by where things go, but within each heading it's more stream of thought... 

Food Ideas    

Coffee  Sugar       Vegetable oil     Hot chocolate   
Salt & pepper       Spices            Creamer
Jam                 Bread             BQ Sauce
Ketchup             Mayonnaise        Marinating sauce
Syrup               Relish            Salad dressing
Mustard             Peanut butter     Cinnamon
Lunch meat          Hotdogs & buns    Bacon
Hamburger & buns    Steak             Sausages
Pork tenderloin     Chicken           Canteloupe
Potatoes            Lettuce           Tomatoes 
Peppers (red, gn)   Carrots           Cucumbers
Corn on the Cob     Bananas (not in mosquito season!)
Onions              Green beans       Apples
Oranges             Kiwi              Grapes
Watermellon         Peaches           Pears
Plums               Strawberries      Dairy    
Pudding/Yogurt      Eggs              Milk
OJ                  Margarine         Sour Cream
Cheese              Snacks            Coolers 
Marshmallows        Pretzels          Cookies
Nacho chips         Chips             Crackers
Salsa               Popcorn           Trail Mix
Beer                Wine              Juice boxes
Soft drinks         Doritos           Chips
Baked beans         Pancake mix       Fajita shells
KD                  Noodles           Bagels
Spaghetti           Alphagetti        Soup
Spaghetti sauce     Liqueurs

In Truck   

GPS 
DVD player
First Aid Kit
CDs  
Laptop
Tool Bag
Two Cell Phones & chargers
Wireless headphones
DVD Movies
XM receiver
iPods
Books
My bike in back
Firewood DVDs and player

• Front Trunk

• Extension cord - 50' 12 gauge   
  
• Extension cord - 15' light duty
• Axe
• Portable rake  
• Potable water hoses (2 x 25', 1 x 10')
• Pressure Regulator
• Towing mirrors  
• 30A adapters (two, one for each direction)
• Wheel chocks 
• Dumping hose 
• Flag and flag pole
• Freshwater submersible pump
• 20' propane hose
• Fishing rods
• Freshwater container & dolly   
• Graywater Aquatainer     
• Folding Chairs (4)
• 12V drill for lowering stabilizers    
• Plastic weave outdoor carpet    
• Box: awning tie-downs, rope light, work gloves, 
• Toolbox: screwdrivers, plastic ties, GOOP, velcro, grommet kit, wrenches, spare bubble level, hammer, wrenches, spare hitch parts, lubricants, etc.
  

Optional, Depending on Trip

• Canoe, bailer, rope, whistle, jackets, paddles
  
• kayaks, paddles, jackets, kit
  
• Extra battery (if dry camping)
• Deep cycle battery charger    
  

Rear Storage Area

• Toy box containing miscellaneous kids toys 
• Four mountain bikes
• Portable air compressor  
• Helmets
• Gloves
• Repair kit & mini pump 
• Bike shorts and shoes
• Kyptonite cable lock      
• Barbecue, stand, griddle
  
• Roll-top table
  
• Levelling boards
• Ropes 
• Tarps (one for bikes, one for rainy weather) 
• Fishing tackle box
• Box of firewood (local trips only) 

Personal Items

• Shirts  (short/long sleeve)   
• Jacket     
• Sandals  
• Sweater     
• Watch
• Hat    
• Running shoes
• Shades
• Reading
• Socks
• Jeans
• Underwear   
• Camping pants
• Bathing suit 
• Shorts 

Bathroom Stuff

• Toilet paper
• Toilet chemicals
• Tylenol
• Band-Aids
• Deodorant
• Toothbrushes
• Toothpaste
• Towels
• Soap
• Shampoo
• Rinsing Cup 
• Hair dryer & curling iron
• Sunscreen
• Bug junk
• Brush/comb
  

Shoulder Season Gear

• Sweaters
• Winter hats    
• Long underwear
• Winter gloves    
• Fall or ski jackets    
• bug hats and jackets
  

Under Front Bed

• Hiking shoes
• Extra shoes   
• Rain boots    
• Water shoes
  
• River tubes   
• Hammocks (2)
• Day Pack
• Bar stools
• Campsite signs 
• Gas lantern, naptha, mantles, funnel

• Inside Trailer

• Beer Skins
• Alum Foil   
• Baggies
• Garbage Bags
• Electric Coffee Maker
• Coffee filters
• Corkscrew
• Garbage Can
• Garbage bags  
• Manual coffee maker
• Slow cooker 
• Large Bowl
• SOS Pads
• Deck of cards
• Spray cleaner
• Hangers
• Thermometer
• Camper Manual
• Utility Knife
  
• Matches & Lighters
• Cutlery and Utensils (incl. flipper & knives) 
• Cups 
• BBQ utensils
• Marshmallow Sticks   
• Dish soap
• Paper towels  
• J Cloths
• Plastic measuring cup
• Flashlights  
• Candles
• Fan
• Fly Swatter
• Broom
• Pots, pans
• Frying pan    
• Pen, paper    
• Clothes pegs
• Plates and Bowls    
• Ceramic heater
• Sheets, pillows, blankets and comforters    
• Rechargeable lantern
• Can opener
• Electric mattress pads (stay on beds)  
• GMRS/FRS radios
• Cameras
• Multimeter
• Toasters (electric & stovetop)   
• Board games  
• Sheets, pillows and comforters
• Weatherradio
• Binoculars
• Whistle
• Compass
• Beach Towels    
• Plastic wine glasses
• Dish Towels 
• Coffee mugs
• laundry hamper
• laundry soap  
• Swim goggles
• Electronics toy box 
• Guitar (old one or 3/4 size)

Under Dinette

• Extra comforters
• Extra sheets
• Extra pillows
• Wiring and controllers for electric mattress pads