Sun Electronics is the cheapest retailer of panels that I've seen bar none:
Solar Panels, Systems, Inverters | Residential & Commercial
They buy panels from manufacturers that have filed chapter 11 and sell them individually or in pallet lots (usually 20 to 25 panels to a pallet). I've seen them sell perfectly good panels at 50 cents a watt in pallet size orders. Be forewarned that their service is reportedly terrible, but you aren't paying for first class service.
Their prices on things besides panels are only average.