Browser extension InvisibleHand has long been great at subtly showing you the best prices for product searches, but now it can suggest cheaper alternatives when searching for airfare as well.
The new flight search features in Invisible Hand are pretty straightforward and simple, much like its functionality with product searches. Basically, you just search for a flight as you normally would and the Invisible Hand bar will show up at the top of your browser's page to let you know it's searching for flights. It takes a minute to get going, but once it's done it'll let you know how many flights it has found and let you know the lower price as well.
If you decide to change your flight information, rather than dealing with the sometimes cumbersome user interface on flight site you're using, you can just change the info directly from the InvisibleHand bar:
(Click image to enlarge.)
It works well with most popular travel searches, including airlines, and should include more in future updates. (I'm hoping for Hipmunk support.) In our tests the most we saved was $US1, but that's a whole app (or a 20-minute phone call in the '90s). Whether or not you actually do end up saving money, this update makes finding flights a lot easier.