Perhaps the best known unknown travel agents search engine (phew), SideStep.com picks up deals hidden in air carrier websites. SideStep works just like FareCompare and Kayak, sifting through itineraries and deals so you can pick out the best price.
SideStep makes it a bit easier to refine your results based on flight times and layovers, and is consistently ranked as one of the best ticket search engines on the Web.
What are some of the ways you find the best deals on the Web?