As a builder by trade, I just can't seem to do anything simple. It is a problem... Here is our coop:
This was built upon a salvaged metal frame. I had an axle welded onto this to accept two 14" heavy duty wheels. The coop is built mostly out of recycled building materials from my own stock and from the Restore (my local recycled building materials dealer.) All of the decorative stars and such are screened over for ventilation.
We have three nesting boxes and one for storage/plumbing (later).
Our flock is new and we have yet to determine how many birds can live comfortably with us. There are four 7 foot tree branches mounted on the inside as roosting boards, they seem to love them. The original idea was to have this as a mobile chicken tractor, but the build got away from me, and although the coop is mobile, and light enough to move around (by me, not by everyone,) I decided to build an 800 sq foot enclosure behind it rather than truly use the coop as a tractor.