We have mashups to help us figure out where we want to go, the best way to get there, and then what's the coolest stuff to do when we get there. One thing that's often overlooked is how much it'll cost us to get from point A to point B.
Go Gas is a Google Maps and TinyLink mashup that determines how much a trip will cost you in gas. You simply enter your start point (HTML5-capable browsers have the option of using geolocation to get the start point) and your course is plotted. Go Gas shows you how many miles your trip is and what you can expect to pay in gas costs.
More at our Go Gas profile
Guia Postos (trans. "Guide Posts")
If you happen to be traveling Brazil, you have Guia Postos. Guia Postos is a mashup that combines Facebook, Google AJAX, and Google Maps to give you a local map, showing gas prices and fuel quality.
More at our Guia Postos profile