[samclem]

Additional info/ideas:
- The window-mount or through-the-wall heat pumps cost about $500 to $700. They typicaly use about 50% of the electricty of statndard electric resistance heating (depending on just how cold it is). Many of these units have a back-up "heat strip" which uses electric resistance heat when the oputside temps get below approx 40 deg F. Yes, it costs more money to heat that way, but I'll bet on those few days it gets that cold, you'd be willing to pay the $10 per day to heat your main room.
Here's a link to some of these units: http://www.airconditioner.com/ROOM_H...NDITIONERS.asp

One other thought: How is your water heated? If you are already using propane to heat your water (and especially if you have a high-efficiency propane water heater), it might be feasable to use your available hot water for a small baseboard/hydronic heating system in a room or two. That way, all te venting and CO problems are avoided (asuming your water heater is installed correctly). A typical domestic water heater is not designed to heat a whole house, but it could be used to pump a few thousand BTUs into a room. This option could be great, but is somewhat off the beaten path and would require a little work/experimentation on your part.