For our trip this Summer to Romania (to visit my husband's family) we had been searching for plane tickets for the best possible price and flight. We ended up finding the best deal for us on CheapTickets.com!!! They have searches where you can type in flexible dates (searching up to 3 days before and after the date you are seeking a flight)! Yes, I know the other sites do this as well, but not for International flights I found. You can flexible search on U.S. flights and Canadian Flights as well but that is all I saw.
We managed to get a good price on three tickets leaving on a Saturday and returning on a Friday! Fantastic! Decent Layovers! We are very pleased with our tickets with CheapTickets.com if anyone is searching for plane tickets!