The Civia Loring rear rack is very nicely built out of tubular aluminum and bamboo.  The natural bamboo decking is treated with multiple coats of nautical grade waterproofing so no mater what Mr Nature dishes out the rack will last.  The Loring rack will work with almost all panniers.  Civia lists the capacity at 40lbs.  

Compatible with 26" and most 700c frames.