That Topeak rack linked by prathmann is an excellent rack for the money. It will not accept panniers with positive locking systems though. No problem really as any pannier with simple hooks will fit fine, including Axiom Seymore.

http://www.amazon.com/Axiom-27-85-Li...N%3DB0028MRKMY

Most bikes will have better riding qualities if the load is balanced front and back.