Skyscanner - Skyscanner.com compares over 1000 airlines to find you the cheapest airfares, fast.
CruiseSheet - Web application for searching for and buying cruise ship tickets.
KAYAK - KAYAK is a travel search engine that searches hundreds of other travel sites at once. Our helpful tools & features find you the information you need to make the right decisions on flights, hotels, rental cars and vacation packages.
Manyflights - Manyflights is an automated flight search service
Momondo - Find cheap flights with Momondo.
JetRadar - Compare flights from hundreds of airlines & travel agencies