Consumerist brings news that TechCrunch (which appears to be down at the moment) has just reviewed the private beta of a service called FlySpy. It looks fairly neat — enter your origin and destination cities, and get back a graph of fare prices for the coming month. You can overlay graphs for different airports, adjust parameters, and generally short-circuit the airlines' confusing pricing schemes.
Or that's what it looks like, anyway (there's a screenshot on Consumerist). The site is still in closed beta. So, on the off chance that anyone has invite capabilities... yeah. Drop me a line.