When pioneers started settling the West, footwear was something that they had to deal with. When the settlers' shoes wore out, they either had to send back East for new pairs, or they had to adapt to Native American moccasins. Some, like the trappers, did so, while others stayed with the hard-soled European-style shoes. Those that converted to moccasins talked about how comfortable they were, and how much easier it was to wear them.
Moccasins are soft and pliable, and let the feet to feel what is under them. They allow the feet to flex naturally (something that barefoot runners advocate) while still offering some protection against rocks and twigs and the like. They also weigh next to nothing, which keeps your legs from doing the extra work.
I've wanted to try using moccasins for hiking for a while. I bought a kit, but they weren't authentic moccasins (they came with foam padding glued inside, which hinders the ability to feel the ground). I made some moccasins out of canvas, but I was worried about the soles wearing out too quickly. I even considered Vibram Five Fingered Soles, a high-tech updated version, but they don't sell them around here.
Then I realized, we've been making another version of moccasins in the U.S. for years now. Small form-fitting shoes with minimum of separation between the earth and the foot. They're called Aquasocks.
You remember aquasocks -- those shoes you wore as a kid when you were playing in or around the water. Made of neoprene, mesh, and rubber, they protect your feet from sharp rocks, while still being light enough you can swim in them. While they're made for the water, there's no reason they can't be used for the trail, or around camp. Yes, they don't offer the protection that a pair of boots would offer, but Native Americans used moccasins for thousands of years (the Salish Indians in the Pacific Northwest oftentimes went barefoot when going through the forests) and the civilizations survived. I've used my aquasocks while scrambling up and down loose scree, and while it tore up my aquasocks, my feet were fine.
I've discovered that I find better places to put my feet, as I can react by feel to what I'm stepping on. I also go a lot faster, as they utilize the natural spring in the step, and it feels like I'm going barefoot all the time. I haven't done a lot of hiking or running in them yet, but I'll keep you updated as I get out more over the next few months.
Price: Between $6 and $10
Build time: As long as it takes to drive to the local shoe store
Availability of materials: Readily available in the summer, but sometimes sold out of your size
Durability: Medium. They won't last long while slogging through scree, but they should work fine in normal conditions.
Functionality: Once you get used to them, they work great.
Portability: If you use them as camp shoes, they weigh very little and take up almost no space.