Seattle-based Farecast, now in private beta, is an airfare pricing comparision tool that also uses a predictive algorithm to recommend when you buy your ticket. So the idea is to show the user not just who has the cheapest ticket, but whether or not waiting might make sense as well. Look for Minneapolis-based Flyspy to launch a similar service in the near future.
I’m mainly linking to this so it’s in my database of intentions. But I also thought it was a cool find – once it comes out of private beta.