List of cheap ways to book flights online?

Alot of times I've seen people post where they got a great deal on a flight on here, then when it's time for me to book a flight, I can never find where the website was listed. How about making a thread of websites people use. Lately I've found good flight deals on:

www.expedia.com (US)

www.statravel.com (US- mostly for students)

I tend to use search engines like kayak.com, cheapflights.com, and orbitz.com, to see who is offering cheap rates at a side by side comparison and then I will always check with the actual airline website.  The airline website itself often has good deals and booking directly with the airline means I can save on the fees of the other websites- even if they're small £10 or whatever.