Dell Home, via its member purchase program offers its Dell Urban 15.6" Laptop Backpack in Asphalt for $28.49 with free shipping. That's the lowest price we could find by $3. It features a large storage compartment, front quick access pocket, external water bottle holders, air mesh padded back, and adjustable shoulder strap.

Update: The price has increased to $33.24. Coupon code "EXTRA15" drops it to $28.25.