Here's an organizational tool most often found in briefcases but now adapted for backpacks: Ivar's Urban 20 Backpack has a tiered vertical shelf system built into the double-zippered main compartment that provides file-like organization (including room for a 15-inch laptop).
The structure has the bonus of more evenly distributing weight and providing better load stability than backpacks with just one big open main compartment. The Urban 20 is 17 inches tall, 11 inches wide and 7 1/2 inches deep and has well-padded ergonomic curved shoulder straps and thick mesh-covered padding on the back.
Besides the three internal "shelves," the bag has a roomy zippered external front pocket, and elasticized side pockets for quick access to water bottles, umbrellas or what have you.
An internal organizational panel on the main compartment's upper back wall has an open stash pocket, two Velcro-closure flap pockets and a slim open pocket for pens/pencils and a hanging key clasp.
Info: Ivar Urban 20 Backpack, which weighs just 11/2 pounds, costs $69.95.