At the urging of a fellow cycling commuter, I'm looking at using panniers instead of my trusty (sweat-inducing) knapsack. My only issue is finding bags that will fit my laptop (13"x9.5"x1.5"), my clothes, and my lunch (no cafeteria at work).

I've read many of the bag threads here but haven't heard any specific references to laptop computers. The lbs near me doesn't have a lot of options to try with the laptop. Anyone have any recommendations?