Here is the web site for upgrade buddy:

http://www.upgradebuddy.com/toolbar/about.html

This is a document that list all the sites we use.
http://www.upgradebuddy.com/docs/cheap_flight.html

How to find the cheapest airline flights
So many different travel websites claim to have the cheapest flights. So, how do you decide which way is the best way to find the cheapest flights. Much of your consideration will depend on how much time you have to research your travel options, and how often you routinely fly.

If you have the time to do plenty of research and you fly often then its definitely worthwhile signing up for ITASoftware's web tool and/or downloading Sidestep's browser add-on. These are great tools that let you see all the fares out there side-by-side.