Excellent commentaries, articles and newsletter at Christopher Elliott's site . These specials are NOT available on any of the pricing sites. They're called 'fare comparison' sites. They take your request and dispatch it to all of the regular pricing sites and give you a consolidated comparison. Even the free version is very useful.
Most useful feature is the ability to shop for price first and then find the available date.
The graphical flight tracker shows the altitude, speed and heading. They discount some routes and on some airlines that Lowestfare does not, and vice versa. They are also becoming one of the premier places to get fantastic deals on international fares. If one website is checked, the other should never be overlooked. Tom Parson's Best Fares web site .