Today, I was looking at flights for a business trip and I thought I would share my favorite travel site: SideStep.com. It searches multiple travel sites to help you find the best deal, but it is really the interface that makes me like it so much. I've never used another site that lets you adjust so many preferences (layover time, layover airport, etc) but it also shows you the effect of your preference on price before you make it and updates your results in real time. You, also, can get results for nearby airports and flexible dates. I think you may need to register for some of the features, but it is worth it.