If you haven't heard of freecycle you should look it up. Its like craigslist, but free! Just one section that everyone posts their haves/wants on, and you can get great things!
I am building a coop right now attempting to spend no more money than the bit it cost for washers to help hold the roof on. I am going 99% recycled materials (gotta use up that scrap wood that came with the house somehow!) The frame for my new chicken run used to be my neighbor's portable garage. Cover disintigrated, so they didn't want it. The door is an old screen door that the screen got torn up on. I will replace it with chicken wire, to match the walls and roof (yeah, hardware cloth is spendy and my dogs keep the yard pretty secure. I lock the chickens in at night too, so run security is not a big problem) I got a HUGE roll of chicken wire from freecycle.
I have lots of misc. building materials lying around, hence my determination not to spend money. I bet you could get lots of free/cheap materials off of freecycle. You just have to decide where on the time-money spectrum you want to be. The more you are willing to spend, the easier and faster it will be to make. The cheaper it is, the more likely it is that you will have to patch, splice, and pull nails out of your scraps to make them useable.
Great things to look for are: old pallats, protable garage/canopy/greenhouse frames, used doors, sheds, dog kennels, and construction sites that will give you scraps.
As far as looking nice, the big thing is how you put it together. And a coat of paint can do wonders!
Good luck!