I don’t think there can be any specific web for US domestic air ticket deal.  It all depends on when you fly and where you flying.  Mostly low fare carriers like southwest, jet blue and air Tran offer good deals but I’ve seen many times American airlines @aa.com and continental @ continental.com offering better deals.  It also depends on the airport, like if you are living at expensive airport city like Cincinnati, you can look for another close airport like Dayton which is less than hour drive and you’ll be surprise by the price difference.