I compost my own stuff because I own livestock. I've been researching how to make hot water to heat a greenhouse and plan on implementing an apparently workable process next year. I'm also looking at bagging and selling compost to the new pot growers springing up all over in Alaska. Pot needs good, rich soil, and compost is some of the best! Who'd have thought you could sell old shit?
I have a book on Colonial Williamsburg gardening techniques. One of the things they did was use composted manure under their cold frames to heat the soil from below. Basically it was a cold frame with a pit under it they would fill first with the compost and then put dirt over it and plant in the dirt.
There are some youtubes on how to make heaters out of coffee/soda/beer cans that might interest you. Basically they paint them black and they suck up the heat and radiate it through hoses. Some examples: