Automatic Waterer
Complexity: Easy!
Cost: it didn't cost us anything because we already had all the materials but I have included what I think it might cost to buy)
Materials needed:
2 five gallon buckets ($3 each at Home Depot or $1 each on Craigslist)
1 small aquarium pump ($5)
drill (or any tool to cut a small hole in the side of one of the buckets)
piece of tubing (length is determined by how far apart you put the buckets)
piece of 2" pvc pipe cut lengthwise (length is determined by how far apart you put the buckets)
gravel or hydroton (hydroton is much easier to carry)
We built this for our quail enclosure but it would work just fine for chickens. We wanted something that would eliminate carrying water buckets, keep the water clean and we wanted the animals to have moving water because it stays cooler and oxygenated that way.
Dig a hole just outside the quail/chicken enclosure. The hole needs to be deep enough to fit a five gallon bucket.
Put one bucket in the hole you just dug and fill the bucket with water (we use either water from a rain barrel or the water hose).
Drill a hole about one inch from the bottom of the second bucket.
Cut a small part of tubing (1-2 inches) and seal one one end in the hole of the bucket.
Fill the second bucket with washed gravel/hydroton about 3/4 full. Put this bucket somewhere insiide the enclosure where the quail/chickens reside.
Let the other end of the tubing just lay on the cut pvc piple.

The cut pvc pipe should reach from the tubing that is sticking from bucket #2 and go all the way to bucket #1, where it will dump water into.

Put pump inside bucket #1 and attach tubing to pump. The other end of the tubing should reach all the way into the top of bucket #2.
We put pond plants on top of bucket #1 (to help with keeping the water clean) and vining plants on top of bucket #2 (something that the birds like to eat). The pond plants also allow us to see at a glance the water level in the bucket.

The quail are so light that they run over the pvc pipe and it is no issue. We are currently doing something similar with our chickens with a few modifications. I don't know if we will have it ready by the September 12th contest deadline so we just submitted our quail one for now. :)
What we would change:
We started with gravel and it was just too heavy and it was harder to work with. We changed to hydroton (we already had a large supply of it) and we LOVE it!
The quail love the running water. We do keep a container of water in the enclosure just in case anything happens with the pump while we are at work. This way the animals always have access to water but they much prefer the running water.