Matt Feeney has been making some nice porteur-style racks under the moniker Pass & Stow, formerly of Liberty Bell fame (a relation?).
One of the key features of Matt's design is the use of vertical supports, which allow panniers to be mounted below the deck. In addition, Matt developed a simple but versatile mounting system that fits a wide variety of forks.
Perhaps the best part is the use of a quick, slick, and secure attachment system for a well designed rack-top bag, made just for Pass & Stow by Freight Baggage. Go Matt.