SkyScanner (Android, iOS, Windows, BlackBerry)

Want a cheap flight? Look no further than SkyScanner. Besides having a smashing interface for dirt-cheap flights, it has a super cool graph where you can track flight fares from anywhere to everywhere. Skyscanner searches more than 1,000 airlines and 1 million routes to find the cheapest flights possible. There are no handling fees and the app allows you to book directly.