If I explain to you how I got the roof up, the walls sheathed, and the siding on, you'll fall asleep before I get to the second paragraph. Instead, let me just tell you what materials I ended up using and why.
For the roof, I ended up using corrugated metal roofing material, which is available at both Lowe's and Home Depot for about $15-$18 per 2' x 8' sheet. It's easy to use, lightweight, and should last a long time. It was a little bit difficult to install by myself, but somehow I managed and I'm still alive to tell about it.
For sheathing, I used 7/16" OSB. Getting the sheathing up on all four walls definitely made the whole structure much sturdier. Before it went up, I was getting pretty nervous that the whole bunkalow would be blown to pieces in our first wind storm. Once two of the four bunkalow walls were covered in sheathing, the bunkalow was super sturdy.
On top of the sheathing, I wrapped the bunkalow in tar paper. The tar paper should help weatherproof the bunkalow a little bit by keeping moisture from being trapped against the OSB and causing it to rot. Tar paper is a relatively easy step and at only about $17 per roll, it's totally worth the extra work.
I knew I wouldn't have enough siding to cover the whole bunkalow, so instead I added more corrugated metal (same as the roof) to the bottom part of the walls. I liked how the horizontal lines broke up the vertical lines from the skirt under the bunkalow floor and I really liked the rustic/industrial feel that it added to the bunkalow's exterior.
For siding, I used old cedar fence boards. Some of them were given to me by friends, some were purchased on Craigslist, and some came from a dumpster on our neighborhood cleanup day a few weeks ago. I cut some of the fence boards into shorter lengths (9"-11") and attached them like shingles to the top of the front and back walls. For the rest of the siding, I attached the fence boards vertically in board and batten style. I used wider fence boards (5'-7") as "boards," left some space between them and then went over the gaps with skinnier fence boards for "battens." The boards and battens are attached with 1" staples. Because the siding is so rustic, the staples are almost invisible, so I was able to