The first thing I do when booking a flight is turn to airfare aggregator
Though Hipmunk is the newcomer to the fare aggregating scene, it has quickly become my favorite (I still rely on and recommend Kayak as it is useful for making comparisons). Specifically, Hipmunk’s site designers have perfected the art of limiting the information on screen to the essentials: flight times, length of layovers, number of connecting flights, and, of course, price, and presenting it in a way that is easy to make sense of and read.
The UI is built so that you can quickly organize and deduce not only the cheapest flight, but also a happy balance between cost and ease of travel (for example, they rank flights by “agony”). Their site, unlike Kayak, sees fairly frequent updates and it was recently improved with the incorporation of built-in tabs; a subtle killer feature that allows you to compare a wide range of dates and airports without having to overwhelm your browser.
Unfortunately for us consumers, the airlines quickly realized that the transparency of their pricing system wasn’t necessarily helping their bottom line. What that means is that you won’t find all the airlines on either Hipmunk or Kayak (Jetblue, Southwest, Virgin, and Spirit are a few airlines that require the use of a proprietary site).
Furthermore, there is a limit to what sites like this can do. They haven’t been all that effective during peak travel times, or for last minute flights. I find that it’s also good to remind myself that spending hours and hours looking for cheaper fares quickly passes the point of diminishing returns.
Looking for cheap airfares is never going to be a particularly pleasant experience, but Hipmunk has, for me at least, made it bearable.
[Note: Both Hipmunk and Kayak now have iOS apps that are good, but not quite as flexible as the website. In a pinch they are highly recommended.--OH]