I use the "Rib Rub Seasoning" from Frisco Spices. I think it is just local to Omaha, NE but you can order on their website. Generally I add about 1 part black pepper for every 3 parts prepared seasoning for ribs and pork butt.
http://www.friscospices.com/spiceblend.asp
http://www.friscospices.com/spiceblend.asp