I just found this site, and maybe I am just late finding it. But this site looks like it has some nice advantages.
For instance, it helps to look at flight prices for about 4 weeks ahead, and looks like this…for instance, Newark to Vegas: http://www.bing.com/travel/flight/flexibleTravel?datelimit2=2009-06-20&depDate2=06%2F21%2F2009&passengers2=1&depPort=EWR&destPort=LAS&submitBtn2.x=21&submitBtn2.y=12
I just started checking the site out, so there may very well be lots of advantages.
If others see things to check out there, post it here.