I often have folks ask me about what gear I carry with me when camping. Many of my friends know that I don't like to take a heavy backpack, not anymore anyway. I have worked hard to trim the fat, eliminating what I don't need while at the same time ensuring that I have what I want.
Most issues around weight can be solved by throwing money at them. Lighter and newer products are coming out all the time. Often there is a trade off between the durability of the product and the weight but it is one that fast and light backpackers are comfortable making.
I'm going to address the big three first, backpack, sleeping system and shelter.
I use the smallest volume backpack for the job needed. I have two different packs. Normally I can get away with a fast and light pack but for bigger adventures, mountaineering that require protection, I have a bigger bag capable of carrying heavy loads.
Choosing the right sleeping bag for the job is important. You need to know what your environment will bring. Knowing if you are a warm or cold sleeper helps a lot too. Mostly, on Vancouver Island, I can get away with my 0 degree down bag and extend its use by wearing clothing or rain gear etc.
Super Ultra Light backpackers will forgo the cooking portion of their trip and so they can save weight in their pack by leaving the stove and fuel at home. For me, I love my coffee too much, I have to take a pot and Cooking system. Typically I'll eat boil-in-bag dinners, nuts and dried fruit, and Clif bars and wasabi peas for my food.
For alpine or anywhere I cannot have a fire -- Jetboil Sol Titanium, 500 g
Water treatment is imperative when in the back country. There are a lot of different treatment possibilities out there but they fall into three categories: Mechanical, Chemical, Light and Thermal. Each carries with it advantages and disadvantages. In my opinion its important to have at least two different methods on hand for treatment in different situation.
Mostly what you carry will be determined by the terrain you are travelling. In this way you'll know what you will need to carry. For instance, will you have to draw water from a much puddle or a slew? Better bring a filter, the particulate will cause problems with most of of the other methods.
There is a lot of information available online already. I don't plan on reinvent it. Here are two comprehensive articles. Bear in mind, these folks want to sell you products. That's okay, you have to drink someones Kool-aide. Part 1, Part 2
Aqua tabs (these are my backup, I carry enough for 5 litre of water but try not to use them)
First aid Kit -250 g
BZK wipes (these are great for wiping armpits too)
breathing membrane with one way valve
toothbrush and Toothpaste
My philosophy around the use of waterproof breathable fabrics is that they don't work when you're moving. If you are sitting at camp or in your sleeping bag they work well but that's about it. I ring the waterproof breathables for use at camp and not for hiking unless it is a torential downpour but even then I'm probably looking for a place to put up my tent of shelter. I hike in a light set of cloths, if they get wet they will dry quick. Once I'm at camp I change into my dry camp cloths and put on the waterproof gear.