http://www.bikeforums.net/showthread...-For-Commuting

I received many good suggestions in the thread above.

My needs/priorities are slightly different from yours. I want a bag that is completely waterproof because it rains like mad here, and is large enough for me to stop at the grocery store on the way home. I don't usually carry my laptop and don't need any special compartment for one. I also wanted a bright and reflective bag, or a material that I could plaster with reflective tape.