I'm experimenting in my basement with a 6.5 gallon bucket sitting in a water bath in my camping-cooler. The bucket is filled to five gallons. It actually fits pretty well, but I can't close the lid on the cooler.
So, I found some styrofoam sheets I had previously used in my old aluminum windows (since replaced) and covered most of the surface area of the water. It's sat exactly at 50 degrees all day, and it's less than five feet from my furnace (it was the best place to put it!)
The goal is to maintain 50 degrees between now and Friday. If that works, then I'll get going on my first lager in the next few weeks.
Fortunetly, my garage stays in the 40's this time of year, so I don't think I'll have trouble laggering it after fermentation!