Slightly tangential, how do you access flight price data? Is there a company providing the feeds? How much does it cost?
Another thought, how hard is it for a travel website that I use frequently to infer that I am from London. I booked lots of fligts in and out from this city. Why not make it my default location after while? Cookies and data mining anyone?
A non-america centric farecast would be good too
I have been using them since before the web (seriously, you could telnet to their system on a vt100).
Unfortunately you can't actually buy a ticket from them! But it will spit out the gobbledygook that a travel agent can use to book exactly that fare, or once you have the specific flights you want to be on you can go through the pain of trying to get the flights on a commercial site.
Of the commercial sites, I prefer orbitz as the least sucky of the lot.
I must've been using Travelocity and Expedia for 10 years now (and easySABRE while it still existed) and I have to say this industry was notable for being ahead of the curve for high-value transactions on the Internet.