If you're just doing some light commuting you don't need a rack/pannier setup for self-supported touring. I picked up an Axiom Streamliner DLX and a Banjo Brothers Waterproof roll-top pannier for my commute and it's more than enough. The Streamliner doesn't really have a usable bed but I like the narrow profile and it's rated to hold 50kg. If you're not going to ride in the rain, you can just pick up some simple panniers from Nashbar.