This year, I made a small rink for the kids in our backyard and I decided to try to make a DIY Zamboni thingy. After looking it up online, I came up with this simple design, which works pretty well.
It's basically just a basic 1 1/2" ABS pipe from the hardware store with a cap at each end and a T in the middle fitted to a standard garden hose. The pipe has several small holes in it and an old bath towel is attached to it.
The other important part is to feed it with hot water. One could use water from a hot tub or some other container of hot water, but I figured connecting the house hot water directly to my garden hose was easier. Only cost a few dollars and some time if you have some basic plumbing skills.