After using a rubbermaid tote that my four girls quickly outgrew (at 3 weeks old), I lucked out and got a free used sandbox on the internets, so this cost about $5 (for the hardware cloth). The rest of the stuff was in our house and backyard.
So basically, I put a loop of cloth around the inside of the sandbox and used duct tape to hold it together and cover the sharp edges. I put bricks around the inside to hold it in place, then filled it with aspen shavings (horse bedding) and put the top on. There's a brooder heat plate and four very content peeps.
Our cats have now discovered the chicks. The cats were pretty freaked out for a bit. Who knew they'd be afraid of baby chickens? They warmed up eventually.
The sandbox is about 4' x 3', and the hardware cloth is 3' high. They've get plenty of room to stretch their wings and run around.
What do you think?