maybe this is different for americans, but isnt google flights quite better than your typical orbitz/kayak? especially so if you're a little flexible on dates with their graphs?
Google flights (or matrix.itasoftware.com, same thing) is ok but they don't have every airline. There used to be a website (which is now a shoddy browser extension) called Flight Penguin, I think there are some similar extensions now but haven't used them.