You may also want to create an account with Fat Wallet, a cash back forum. I recently priced airfare through the major airlines, Kayak, Expedia, Orbits, etc and with the cash back deal at Fat Wallet, I would have saved about $35 booking thru Expedia. The cash back is slow but money saved is money saved.
Cheapest prices are typically released on Wednesdays and according to several sites, mid week travel is not cheapest. Saturday travel is. My guess is business travel is more prevalent during the week.
