Travel Aggregators

I find Sidestep to be not unlike Farechase - they separate fares by time of day, and have a very user friendly setup for finding one way or roundtrip airfares.

Their best airfares are often similar to Farechase as well, they just don't always match Kayak.

Sidestep

A few points about Sidestep -

• toolbar option
• lots of travel deals listed on a separate page
• similar breakdown of fares to Farechase including time of day
• straightforward setup for one way or return airfares
• flights originating outside of the U.S. are priced in USD