Simply try out the air search of this site (metafares). There you have to fill in the search form with your from and to locations, the date when you want to travel, then select the travel sites from which you want to see the results. After clicking compare you can very easily see which site offers the cheapest rate. - (2007-10-17)
You can try the metasearch engine that travelgrove.com have. - (2007-10-17)
Do the search for the airfare here in Metafare as well as other large seach sites like Bookingbuddy. These will compare the major sites against each other and it is suprising that the price changes depending on the site and comparision link. Also check the box with neighboring airports to see if there are any savings that you can take advantage of. Early morning flights are better than after 9 am since business travelers start then. Also staying over a Sat. night will decrease the cost. Some sites have a box to check that will compare prices on the day before/after and give you a box comparision to allow you to choose the best time for cost. Good luck. - (2007-11-26)