I posted this in the Colchicum thread, but I thought it was worth putting it here also. If you've got a big cardboard box, some tall bands, and a couple of plant trays, you can put this together. The heat source is an incandescent lamp. You'd better buy a few before the energy police ban them.
I've used this to break the first dormancy of delayed hypogeal lily seeds, and to start tomato, pepper and eggplant seeds. The eggplant seeds simply refuse to germinate below about 75 degrees F. But you need to keep a close watch, because the seedlings will quickly elongate and become useless if you leave them in the box after they've germinated.
To keep the potting mix moist, place the seed pots inside a plastic bag and seal.
If you want to get fancy, it's handy to have a thermometer that you can stick into the potting mix. If you want coarse control of the temperature, change the light bulb wattage. For fine control, hook up a cheap light dimmer.
Disclaimer: if you are a complete klutz, please do not build this thing. You can electrocute yourself or burn your house down. I would die of guilt.