Here are updated articles for 2008 from AirTravelGenius looking at the price differences between major Online Agents for various international flights.
For US agents :
Expedia vs Travelocity vs Orbitz
For UK online agents:
Expedia vs Lastminute vs Opodo vs Ebookers
The articles conclude you should always get multiple quotations to get the best airfares.
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This post first appeared on TravelGenius Blog - Air Travel Tips | Cheap Flight Airline Deals, please read the originial post: here