[markem]

Another thing to consider is that when it gets really cold, open the cabinet doors below the sinks. This allows warmer air to get in around the pipes.

All my pipes are insulated, but since I'm in relatively warm western Oregon, I don't have any electric wraps or such for the pipes.

All you southerners - also consider turning off the water to sprinkler systems and then draining the system. Lots of people forget that in areas that don't freeze often (like some of my neighbors).