Sort of a airline price aggregator, Fast Company Now has a post that links through to Mobissimo. Since I happen to be planning many trips, I tried Mobissimo vs. Expedia. Mobissimo was never significantly cheaper than Expedia, but think the Google landing page vs. the MSN landing page and that gives the perfect idea of how much more no-frills and direct-to-the-point Mobissimo is to use.
Mobissimo returns results from all kinds of major sites and lets you know which site is providing the best price and who the carrier is; results are automatically ranked from cheapest to most expensive. Additionally, there is a cool e-mail option that allows you to shoot the fare information directly to someone else via a simple java script application.
Note that Mobissimo does not actually handle any of the ticket purchases for you; it only redirects you to the site of the ticket that you pick. Further, note that Mobissimo pulls prices from non-US sites that charge in foreign currencies.
Pretty cool find.