Have a look at the Flyspy alpha. They have put together a very impressive series of data points to show in a simple graph changes in price by departure date. In Web 2 speak it is an air search mashup. Podtech have an interesting podcast interview with the founder. Fascinating that one guy has found a way to display complicated flight info and options that (while data heavy) provides better price vs departure date guidance than any of the heavily tech staff stocked big guys. Will keep a watch to see if this comes out of Alpha.
UPDATE - Fast Company have a quick note here