You can use the google.com website (and only this for now, the local ones are not showing the results) to find flights for a certain departing and returning time.
You simply enter a search in the format “From town1 to town2″ where both towns have to have an airport and direct flights between them.
From New York to London would be a valid request.
Google then shows as the first search result a box in which you can enter departing and returning time and below that box a link to the websites of Expedia, Hotwire and Orbitz.
You simply select one of the three and are forwarded to a booking page where you can book the flight.

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