I'm always looking for simple systems that work well. Passive houses seem like a great innovation: they are so efficient that they do not need furnaces and are heated by the occupants and other equipment in the house itself. A special heat exchanger allows a steady exchange of air with the outside to keep the house ventilated yet warm.
Unfortunately they are still too cutting edge in the US to make them practical but they are doing well in Germany.
Read more in the Dec 27, 2008 NY Times article: No Furnaces but Heat Aplenty in ‘Passive Houses’