Cheap and Easy Heatloss Detection?

Monty asks: "I'd like to measure heat loss to find out where to insulate and then find out if that is working. What can be done cheaply? Can I use my Sony's Nightvision and just cover up the IR emitter? Are there cheap but useful infrared cameras? What about plain infrared film? Or how about temperature data loggers? Where's a good place to ask these questions?"