Also, pay the money for high-quality bike-bags. Backpacks get sweaty like hell; something like Ortlieb bags are water-proof, light, stable and fit a backpack. You can also get bags with laptop padding; but I just tend to throw my backpack into a standard Ortlieb.

The Ortlieb bags less expensive in Germany. Americans should probably look for a local brand, if any good exist (or find some way to import them yourself instead of paying crazy amazon.com prices; inside EU you can get ortliebs shipped from any German retailer).