I just finished our under-$100 coop today. Our girls are about 2 months old, and we had them in a giant rubbermade tub setup until today, when I moved them into the coop. I know you said you prefer pictures but my wife is out of town with our camera. So I will explain with words and maybe post pictures at a later date. Maybe send me a message later and I can post crappy phone pictures on the internet for you to see. For what it's worth, I've lived in Portland, OR and Eureka, CA, so I can imagine what a coop would need in those areas. Make it waterproof!
Best advice: scrounge lumber! The free section on Craigslist and re-purposed building goods stores are good. I work in construction/carpentry, so I have the opportunity to get free lumber and building products when we demolish parts of homes that are being remodeled. Maybe you have a friend in that line of work. Here in Denver, there's a place called The Lumber Guy that sells scratch and dent lumber for cheap, and you can haggle. Find a place like that. Or when I lived in Portland, there was a store on the hip stretch of Milwaukee Street that sold salvaged building and architectural stuff. Sometimes Habitat for Humanity has stores like that, too, but not in all cities.
Small tips: Cut up bicycle tubes make great weatherstripping for doors. Our friends swear by them. Or get the strips of sticky-backed foam weatherstripping at Home Depot (I hate buying from them) for $3. Cut off ends of lumber work well for holding open lids (like on our nest box) and windows. Look for people in your neighborhood getting a new fence installed - where is the old fence? The 4x4 posts and 2x4 or 2x2 stringers from the old fence are great for building a coop. In fact "furring strips" (also Home Depot, yuck), are super cheap and for our small coop - built to house six chickens - I didn't need 2x4, except in a couple of important structural locations. I haven't had much luck with Freecycle, but some people swear by it. It's a group/listserve thing that you have to sign up for and it seems like a more reliable version on the free section on Craigslist. I just made a feeder and waterer out of PVC pipe today. The cost was cheaper than pre-made versions. You could also do the 5-gallon-bucket watering system instead of buying what is exactly the same thing for much, much more. Any home-improvement store sells stick-it flooring tiles (12"x12") for 25 cents or less. I put them over my plywood floor so that cleanup will be easier in the future.
I did have to buy a few things. You don't really see used and still actually usable roof shingles anywhere. They get destroyed when you tear them off to replace the roof. I had to buy a pack of shingles, but I suppose you could probably find corrugated plastic roofing used or free. I have been unable to find wire fencing/chicken wire as of yet. That stuff is expensive, so we're free ranging for now, and I plan on making sure they are in the coop a little before dark - there is a fox in our city neighborhood that cruises our alley about once a week. You will have to buy screws and nails and door latches, but those won't break your budget.
Things I already owned that made life easier: a cordless drill, a circular saw, a chop saw, building (specifically framing) knowledge. If you don't posses these things, try to find somebody you know or an acquaintance who does. You'll have to pay for the labor, of course, but at least you'll be able to provide the free or near-free materials. If you have enough hens maybe trade a weekly supply of eggs to defray the cost.
Notes on your post:
I wouldn't use plastic sheeting for a roof. There's no sure-fire way or making sure water doesn't creep under the plastic and soak into the wood of the roof, or into the coop itself.
I have seen "buckets" for nesting boxes - they are actually pre-made and manufactured specifically as nesting boxes, but they are kind of expensive.
Your birds ought to have all their feathers by the time it gets cold in the State of Jefferson, so they should be cold-hardy.
You could use your tree limbs for the structure, but if they are freshly cut, they will dry out and shrink, loosening all the screws or nails and essentially ruining the structural integrity of the coop. Ask a timber-framer about such things.
