I started looking at lightening my load a few years ago, and really jumped into it this year. I used to carry anywhere from 40 to 70 lbs, depending on how long I was going to be out. With the heaviest packs I've had as much as 16 days food. My goal has been to get my pack weight down to under 25 lbs for a week. I've reached that goal but I'm now looking at getting it down to under 20 lbs, or as close as I can get to it. With a lightweight pack I'll be able to hike further each day, and feel a lot better. The largest weight savings can be made with your backpack and tent. Previously my backpack, tent, sleeping bag & pad totaled about 15 lbs or more. I'm now looking at about 6 lbs for the same items. After you've gotten your pack weight down as far as you can the only way to save more weight is to hike with other people. That way you can share community items such as a first aid kit or cook kit.
One thing to remember about lightweight gear is that there are trade offs, and some people might like them. If you're one that doesn't take much care of your equipment, and throws it around, then lightweight backpacking isn't for you. If you don't like sleeping out on the ground but have to have a tent then it isn't for you either. Most lightweight tents are nothing more than a tarp with some netting. Theres no false sense of security that you're protected from everything.
When you start looking for lightweigth items you'll find most stuff online. Most sleeping bags can be found in stores as well as some smaller items such as silverware, pans, first aid kits etc. Go out and buy yourself a small scale that can be zeroed out. Some larger items will have to be put in a box to weight. Put the box on the scale and zero it out before you weight different items. As for backpacks and tents you'll find brands such as Granite Gear and GoLite in stores, but thats about it. You'll find some real nice equipment online. Some of the best stuff is made in garages. ULA recently closed for 6 months while he went backpacking. When he delivers orders to the post office he likes to use a trailer behind his bike. Overall ultralight backpacking is a grassroots industry. Below is some of my observations about products.
Fabric Mojo - Mountain Laurel Designs has some good info on fabrics. Find out the difference between Silnylon, Spinntex Event or eVENT.
Tents - People use tents for one of two reasons. One being to keep insects out and the other to provide protection from the rain or morning dew. I think some people get a false sense of security from tents, but it won't keep a bear out. I currently use one of two tents, both from Henry Shires at Tarptent. Lightweight tents tend to be single wall tents which have their downside. Single wall tents are prone to condensation on the inner walls. Their best set up so that a breeze will blow through the tent, taking the moisture away. I've had problems in areas where the ground was very saturated from several days of heavy rain, and no wind. Many tents don't have a floor. I always use a tarp to protect the floor of my tent so in reality I had two floors so I have no problem using a floorless tent. Tarptent and a few others have netting that hangs down on the sides to keep insects out. You tuck the netting under the ground sheet. Weight it down with rocks, shoes etc. One concern about lightweigth tents is that on real windy rainy days you could get rain blowing in. This could be a problem. The only thing you could do is to lower the tent as much as possible. I do know that my Traptent works great in heavy rain, and I mean heavy!
Ground sheet - One word. TYVEK. Tyvek is available from serveral websites and is sold by the foot. Cut it to the width you desire. There are other brands that are similar. Its lightweight, tuff and waterproof. Its harder to rip than other products.
Tarps & Bivy Sacks (or sac) - If you want to save more weight you can use a bivy sack. Basicly there are two kinds of bivy sacks. Those that are fully waterproof, and those that are water resistant. The fully waterproof bivy sacks are just that, and weigh more. Most are at least two or three pounds but some are as low as about 20 ounces. Water resistant bivy sacks need to be used with a tarp to provide protection in the rain but they'll protect your sleeping bag from morning dew, and the ocasional . Tarps can be small since the bivy sack protects from spray. Some bivy sacks fore go things like side zippers and bug netting to save more weight and use a draw string to close it. Many people don't like the bivy sac laying on their face while sleeping. In that case look for sack with a wire hoop to keep the bag off your face, or a tarp with a tie point over your head. Some sacks have a loop that will allow you to tie to the loop on the tarp to keep the sack off your face. The water resistant bivy sacks usually weight between 4 1/2 to 11 ounces. I've been looking at one from Mountain Laurel Designs that has side zips and bug netting and weights 7.5 ounces. Combine that with a tarp that weights as little as 2.9 ounces and I can save almost 9 ounces from my lightweight solo tent.
More about tarps - Tarps come in a variety of shapes. The basic tarp is a rectangular or square shape. These are the cheapest ones and can be set up in various ways. The more expensive ones have a catenary cut. This means that back of the tent is lower than the front, and narrower. This allows the back of the tent to hug the ground and shead wind, but gives you more headroom. The height of the tarps depends on how you put it up. Most people use their hiking poles, a stick they've picked up or tied to a tree. Items you might find on various tarps are reinforeced tie out points or a loop to tie the face of your bivy sack to.
Sleeping Bags -Syntetic or Down? Thats basicly your choice. Down is lighter, but is a problem if you get it wet. Down is rated in pounds of fill. An 800 lb fill means its got 800 cubic inches of loft for each pound of feathers. The more loft the warmer it is, and more money. Most sleeping bags are about 700 lb fill. If you're hiking in the moutains you'll want a bag rated at temperatures of 20 degrees or lower. Vapor barriers are hard to find, but can add 10 degrees to that for little weight and money. I find that I have to wear long underwear in them but if its too cold its worth it. You might find that the lighter bags tend to be cut narrower so if you roll around a lot you might find it constraining. Synthetic bags are easy to dry when wet, heavier, don't compress well and are cheaper. Two of the best brands of lightweight sleeping bags are Western Mountaineering and Feathered Friends.
Rain gear - Gore-Tex is heavy and expensive. I don't care what people think, if I'm hot and sweaty while backpacking Gore-Tex will never be breathable enough. An alternative is gear like Frogg Toggs, which is suppose to be more breatheable, and a hell of a lot cheaper. I haven't used them but I've read comments from other hikers and I'm interested. They do rip easier but a bit of duct tape will fix it. People have said they've use them for a year and then thrown them away after buying another set. I prefer ponchos which allow better ventalation and are lightweight. Combined with gaiters its usually all I need if its warm enough. Something new I want to try is ULA's Rain Wrap. Its basicly a skirt to wear with a rain coat and probably gaiters. The heat from your body escapes out the bottom so you'll stay cooler. It can also be used to cover gear at night. I've only read good things about it and at 3 ounces its hard to beat. A rain coat and pants can also be used to keep you warmer at night, or to keep the wind out.
Shoes - With a lighter backpack heavy hiking boots really arean't needed unless you're really worried about twisting an ankle. You're feet will be so happy with proper fitting hiking shoes. Make sure they're stiff enough to protect your feet from walking on rocky trails. You may want to get some gaiters to keep small rocks and sand out of your shoes. Lighter shoes equals happy feet equals more miles per day. Leave those camp shoes behind unless you need something for creek crossings in which case maybe you'll need some Crocs.
Stoves - If you're hiking alone or with one other person look st alcohol stoves. They weight about 1/2 to 1 ounce. You measure out a certain amount of fuel and poor it into the stove and light it. Once its used up thats it. Don't try adding more fuel until its cooled down or you might get hurt. Knowing how much fuel to use is something you have to learn. You can even find instructions on the internet to make your own. Just search for a Pepsi can stove or a cat food stove. I bought a stove from Anti Gravity Gear and got a Caldera Cone also. The cone wraps around my pan to keep the heat in. I can carry it in my sleeping pad which lays flat in a slot in my backpack.
Water Treatment - You have two choices, Chemicals or filters. Chemicals don't always kill Cryptosporidium, and with some you have to wait 4 hours. Cryptosporidium isn't always a problem depending on where you go. They do take care of the other things you have to worry about. I love the Hiker filter! Light and fast, but I'm probably going to be using Aquamira on my next hike. I'm not sold on the new haolgens or Steripens etc. Too easy to break. Then what do you do?
First Aid Kits - Do you really need to carry those heavy kits around? Get a lighter one. Better yet, take a real wilderness first aid class!
Flashlights - you'll probably be going to bed soon after it gets dark. All you really need are LED lights. The ones made for key chains are plenty. It puts out enough light for me to see the bears eyes in the light, and I can still read a book. Nothing like shining a light around and seeing 5 sets of racoon eyes looking at you, waiting for you to leave some food out. LED lights also mean less batteries since they last so long.
GPS - don't bother. Learn to use a compass!
Clothing - get your scales out and weight everything. Use the lightest stuff. Don't carry two sets of long underware. If it gets too cold crawl into your sleeping bag. I prefer to buy clothing at a store so I can try it on. A large from one company might be a different size than a large from a different company. If you do buy clothing online make sure you check their size charts! NO COTTON! Cotton can kill you if it gets wet. I do like sleeping in a cotton t-shirt though but for long hikes I'll be leaving it behind. Take a scale into the store if you have to. Some of the lightest coats use a fabric that will rip easier. Not something you want to happen if you're going to be in areas with lots of brush.
Duct Tape - Carry a small pack of Duct Tape just in case. It has many uses such as fixing rips in your coat or tent. You can also use it on your feet to prevent blisters. I've also read about it being used to get rid of warts.