The most popular way to store items such as extra clothing and various accessories while camping has been stuff sacks. I was amazed at their prices, often over $30, and wondered why plastic bags from your neighborhood grocery store couldn't serve the same purpose. I came to find that stuff sacks claim to serve two additional needs for camping bags:
1) They need to keep everything dry - very important for clothing
2) They need to compress down to a small size to be able to fit into your pack.
3) Some bags claim to provide extra stitching and odor control for keeping out critters.
Its clear that both of these needs are really only essential for clothing and food. I personally decided to use a bear-proof container for my food/suntan lotion, because I didn't really believe that simple stuff-sacks could keep out rodents, which are typically your biggest nuisance, and to provide a bit more food security and isolation.
So that leaves clothes, and everyone who has camped while it rains or snows knows that if your clothes get wet, you're pretty much screwed. It was in thinking about 2 things, cost and dryness, that I thought about the ultimate solution for keeping moisture out ... Vacuum sealed bags.
Step 1: Vacuum-sealed bags
The crux of this plan however, is how do you actually vacuum the air out while you're out in the woods.
Step 2: Ziplock vacuum pump
I got this starter kit for only $5 online on amazon, and am not sure if it can be found in any grocery store.
Step 3: Put stuff in, pump out air
1) Your clothes will conform to whatever shape you had them in when you started pumping the air out, and the bag will become as hard as a rock. If this means you want to fold your clothes to keep them flat, or just stuff them rounded, depending on how you want them to fit in your pack.
2) If you have very few clothing items in the bag, i.e. they don't fill the whole bag, make sure that the one-way valve is directly over your clothes. If the valve is already pushed up against plastic, it won't vacuum very well.
I consider this both short and long-term storage. It only takes about 1-2 minutes to pump all the air out, which is a small price to pay for dry clothes.
For the clothing items in this instructable, it only took me about 15-20 secs to pump out the air.
The bags are very durable enough so that I do a trick using my whole pack.
Step 4: Whole pack trick
I basically use the larger vacuum bag now to line my pack, and I do these steps to save space:
1) I put in my sleeping bag, hammock and whatever else, and close the ziplock on the bag to 'almost' closed. (Leave the vacuum valve open)
2) I step/put weight on the bag until I get as much air out as possible, and close the ziplock
3) If you're lucky, the vacuum valve will let you push air out by putting more weight on the bag. Sometimes the valves work this way, sometimes they're more touchy. There's no use using the pump here, it would take ages to pump out all the air.
While this will not completely vacuum seal the bag, it will at least save a ton of space. While there is technically still air and thus water vapor present in this un-pressurized bag, it is still thus susceptible to moisture, but on a far less degree than any stuff sack, and much better than if the sleeping bag was just sitting in your pack. I personally have never had my sleeping bag or hammock get wet under these circumstances.
All in all, for about 10-35 bucks you can have a vacuum sealed system for camping.