I just read about Momondo's Flight Insight (had never heard of Momondo until I saw this article admittedly) but Flight Insight is a pretty cool use of data.
Momondo Introduces Flight Insight
Travel search engine momondo announced the introduction of its Flight Insight feature in the U.S.
Flight Insight aggregates data from thousands of fare searches to provide individual users with a unique analysis that will help them figure out the most advantageous pricing and timing for a flight...
I've been playing around with some potential flights and if you are really flexible in terms of when you can go, you could save a bit. You don't even necessarily have to be flexible to take advantage of one fact the system presents, which is which day is it cheapest to buy a ticket for this route on.
Of course, it's only based on searches done by Momondo users but it's still kinda cool IMO. Another limitation is it only works on a limited number of routeds so about half of my searches didn't have any insights.
Anyone else try it yet?