My better half said she wanted to learn to use some tools so I let her do most of the work on this. It's pretty simple and not terribly expensive. Some PT 2x6s and 2x4s, a couple of 16' cattle panels and it's about done. She built a doorframe from 2x4x and used the little triangles of wood at the bottom center of the pic to brace the corners of the door. Some hinges and a bolt completed that. I used 48" wide 2"x4" welded wire to make the front and back and regular chicken wire over the top. She also made corner braces from some scraps I had so it will hold it's shape better when we move it.
I'm going to cut a square hole in the front so we can put one of the free dog houses I got off craigslist up against it to make a nest box and shelter from bad weather. The dog house will have a door in the back to get the eggs out and I'll put a hinged door above the opening so I can move the dog house separately from the chicken cage. I'm going to add a roost pole to it as well.
When that is done I've got some wheels off an old tricycle I'm going to mount on it so it will be easier to move around and make it like a giant chicken tractor.
I found this idea on a DIY forum. The original idea was for a greenhouse. The original had a base made from 4x4s, which made it easier to build a regular doorframe. The advantage of the 2x6s is that I didn't have to use big bolts to hold it together. Large fence staples hold the cattle panels in the base. The corner braces go over the ends of the panels and help hold them in.
If you have the materials on hand and you can work without interruption you could easily finish one of these in less than a day.