I think any decent rack should work fine. I have an older Axiom Odyssee on my commuter. The Topeak Explorer rack usually gets high reviews as well.

As far as panniers go it is really up to you. The Nashbar house brand seems to be pretty good band for your buck. I have the Axiom Kootenays but have rarely used them. I have a milk crate attached to my rack so I can throw my back pack or groceries in it.

It sounds like you want something you can take on and off and carry around with you. Perhaps attaching a rear basket to toss your back pack into would work fine. Another option would be the Wald carrying baskets and dump your back pack into that.