I have a Phoenix Technology Kick Light 6 position stock on one of my shotguns. I love it. It cuts about 30-40 percent of the recoil out. This is if you don't mind a pistol grip style stock. Its the same concept as an AR15 type stock. Here is an address to amazon were they sell them prolly cheaper than anywhere I have found.
the problem is catching them in stock with all this proposed gun ban hoopla. Also, I have it on a Mossburg Maverick 88. Just the cheaper model of the 500.