Best sites for travel booking?

I'm planning a trip to Rome in the summer. We are going through a tour group but need help finding the best deals on airfare. What are some good, reliable sites to find airfare deals from the US to Europe and within Europe?Best sites for travel booking?
You can check out http://www.kayak.com or http://www.skyscanner.net.
Most of the time, I book on the airline website itself. While it might be true that you could fine one cheaper on websites such as Expedia, I have yet to have a great success on it. I do, however, book with American Express while I'm going on intercontinental because I can get 2 for 1 business / first, but this often applies at the very last minute of travel..

You probably should look at Lufthansa, Swiss, Ryanair, etc etc...

Best wishes,Best sites for travel booking?
Any of the big travel sites will be your best choice. They all will quote you approximately the same price, give or take $1. However, once in Europe, depending on how fast you need to get from point A to point B, consider the train system as an alternative.
I book on the airline website itself. While it might be true that you could fine one cheaper on websites such as Expedia, I have yet to have a great success on it. I do, however, book with American Express.
Kayak or expedia is always my top choice. I wrote an article below on cheap air that may help as well. Facebook me if you have any ?s