I have to drag my laptop around too because I work for myself. But I only go to one client. I wish I could pop the stuff on a stick but I can't.

I was looking at panniers and then realized that I can just bungee my backpack to my rack on the back. I use three bungees and really strap it down. It doesn't shift at all and I can put everything in it. I'm thinking about getting one of those baskets for the back instead but for now it works. I didn't want to drop the cash if I didn't really commute like I wanted. You have to tuck or tie up the straps though or they will flop down and get caught up in your spokes.