I highly recommend that backpackers work from a camping list as they plan their gear purchases and pack for their trip. There are two reasons for this. The first and most obvious reason is that if you forget something important, you can't hop in the car and run to the nearest Wal-Mart to buy a replacement like you can when you're car camping (I currently own 3 propane bottles due to this phenomenon). The second and less obvious reason is that it helps you limit what you bring, which is very important when you're carrying everything on your back.
Below I'll show you my list. Granted, I'm not a thru-hiker, nor have I done 4-season backpacking, but I have done a couple 11-day treks and many shorter trips, and this is what works for me:
Shelter
Most backpackers use tents of some type. I have a Coleman Cobra small two-man tent that I use when the weather is really cold (I had dreams of being chased by a Polar Bear jumping from iceburg to iceburg one night when I tried sleeping in my hammock on night then the temperature was hovering around zero). I've found, however, that when the terrain, the rules, and the conditions allow, I prefer using a hammock. I bring the tarp for shelter over my hammock, and it has served at quick shelter for a group of nine during an intense sudden storm that came up while we were on the trail. Obviously, if you're going to be camping in very rocky terrain, you'll want a free-standing tent. If you're going to be hiking in heavy snows, you'll want a four-season tent. Here's my shelter:
Kelty Noah's Tarp 12 (I considered a 9' tarp, but to me the 9oz difference was worth it for storm protection. It's very roomy for one person. I've also shared my tarp on occasion. There are lots of tie-outs, so I have plenty of options for set-up.) 40"x96" polycryo groundcloth (very light and folds very small)
Sleeping
Ultralight fanatics would never be caught dead with anything but the absolute lightest down sleeping bags. More power to them. All of my bags are synthetic. I live in an extremely rainy area, and synthetic bags still provide loft and warmth when wet. Due to one unfortunate incident on a Scout trip, I spent a cold night in a bag after wringing it out and other than being a little clammy, was fine. Down, on the other hand, loses all loft when it's wet. Granted, there are lots of ways to keep your bag dry, but I'd rather prepare for the worst, so I suffer with a few extra ounces and a slightly bulkier bag.
Homemade hammock (I can't always use it, but it's nice when I can) 3/4 length Thermarest Guidelite (I can use this on the ground or in the hammock for bottom insulation if needed. I also use it for a "chair" on occasion.) Sleeping Bag (I have several and bring the one that's suited to the weather) Sleepwear (ranges from underwear in warm weather to silk long underwear plus wool socks and a beanie in cold weather)
Pack
Some people prefer external frame packs, some prefer internal frame packs. Here are the key differences: an external frame pack is cooler on you back and you have options on how you attach gear to the outside of the pack, but it tends to ride a little further from your back than an internal; internal frame packs ride very close to your back which really reduces load swaying, but they're hotter on your back and there are fewer options on how to carry your gear. I prefer internal frame packs, simply because I haven't found an external frame that doesn't hit the back of my head as I look up. I have a couple of packs, but my current pack is very light, since this is a good place to really trim the pounds.
Gossamer Gear G5 Hyperlight pack (I wouldn't recommend this if you are hard on gear, but I've found it to be fine for me.) Rain Cover
Water
I've heard of groups running out of water on the trail. I'll do everything in my power to make sure that doesn't happen to me or a group I'm hiking with.
Depending on the water supply in the area I'm hiking in, I will bring two Nalgenes, a four-liter Platypus water bag, and if needed, two empty one-liter club soda bottles. Note that if you're in bear country and your water bottles have ever held anything other than water (club soda is just carbonated water), they should go into the bear bag at night. The food smell permeates the plastic.
Aquamira Water Treatment
Cooking/Eating
There are lots of options for lightweight high-tech stoves that are available today. I made the alcohol stove after reading an article online, and since it's pretty cool and tends to be a conversation starter (not to mention being very, very lightweight), it's what I use. Obviously if you're going into an area where you have to rely on available fuels, stick with one of the more common white gas stove or even a dual fuel stove that can also use unleaded gas.
Homemade soda can stove + windscreen Small bottle of methanol for fuel Aluminum pot (grease pot) Titanium mug Lexan spork (gotta have a spork)
Safety
Skimp on your tent, and you get wet. Skimp on your sleeping bag, and you'll be cold. Skimp on your safety equipment, and you could die.
Survival Kit (always in my pocket) First Aid Kit Lighter, "waterproof" matches, and a magnesium firestarter (there have been many cold, wet, windy nights where the magnesium turned frustration into fire) Headlamp Two Pulsar LED lights (one is always clipped to the outside of my pack) Topo map Compass (I don't need no stinkin' GPS - I will bring one, however, if there are any GeoCaches on the route I'm taking)
Accessories
Some people bring less, some bring more. I've found through experience that these are the items I use, and also those that I regret if I don't have.
Trekking Poles (they REALLY help when you're loaded down with water in rugged terrain and they can be used to pitch the tarp on the ground) Journal + pen + 2 golf pencils (I lost my pen and my backup pencil once. The pencils are very light.) Bear Bag Cord Several homemade stuff sacks Camera (I've been bringing a small digital with lithium batteries. The lithium batteries last a LONG time.) Sunscreen Bug Repellant Bandanna Toilet Paper in a freezer ziplock Plastic trowel (sometimes the ground is just too hard to kick a hole with your boot) Crocs for camp shoes Bottle of Dr. Bronner's Peppermint Soap Lightweight wide-brimmed hat Lip Balm Baking soda (for toothpaste) Compact toothbrush Small bottle of hand sanitizer Sunglasses with neck cord Watch Rain Jacket and Pants Trash Bag(s) (I normally bring two in case one gets punctured. I also compact my trash very well, so small bags work fine for me.) Duct Tape - a couple of yards wrapped around one of the Nalgenes is enough for me. Multi-tool (the pliers double as a pot lifter)
Food
Please keep your food and trash completely separate from the rest of your pack items. Gallon Ziplocks will work OK for this. You don't want your pack or gear to smell like food. Bears have excellent noses!
Two hot meals a day - oatmeal for breakfasts and variety for dinners Cold trail-type food for lunches/snacks. (Make sure you plan for plenty of calories or you're really start feeling it in the middle of your trek.)
Clothing
I'm not going to list all of the clothing I bring, because it changes significantly season-to-season. However, I think it's important to list the clothing items I pack (i.e. duplicate items):
One extra wicking t-shirt Two extra wicking underwear Two extra pairs of Smartwool socks (I know I wasn't going to get into clothing specifics, but I have to mention these. I've found the Smartwool Trekker socks to be the best for backpacking. I bring three total pairs so that I always (hopefully) have a dry pair to change into.)
Optional Items to Consider
You may think of other items you want to bring, but please remember that an ounce on your back is a pound on your feet!
Sock liners (I hate them, but some people love them. With Smartwool socks, I have no need.)
Gaiters (I've never used them, but I'm sure they help keep your socks dry in foul weather. They're on my "should try" list.) Extra Ziplock/trash bags Feminine Products (Backpacking can make your cycle go wacko, so be prepared) Reading Glasses, if needed (how else are you going to read your map?)
A Sharpie marker Extra glasses, especially for contact lens wearers; extra contacts; contact solution
Deodorant (not recommended in bear country - you really don't want to smell interesting to bears)
If you use the above camping list as a guideline as you prepare for your next backpacking trip, you can insure that you bring what you need without carrying a lot of stuff you'll never use.
