A discussion of the design of the small National Geographic Walkabout Rucksack.
You can configure the dividers to accommodate your equipment, though I find this type of scheme--narrow strips of Velcro and fairly stiff padded dividers--never seems to properly fit bodies with longish lenses on them, just small consumer bodies with 18-55mm kit lenses or shorter. They're good if you have lots of compartment-size things, like lenses and flashes.
For days when you don't need a camera, you can take out all the dividers, unzip the separator between the top and bottom compartments, and use the Walkabout like a typical backpack. The bottom flap has another flat zippered pocket on top with nylon holders for cards and pens. The bag lacks storage for media cards and other small accessories.
On of the best things about the small Walkabout is its ability to accommodate a 12-inch notebook. Most small bags lack this amazingly convenient back pocket, which you can also use for letter-size papers.
The Walkabout is made of a sturdy, attractive brushed canvas fabric. Though it's not waterproof, it is water treated, and it comes with a plastic showercap if you get caught in a downpour. Unfortunately, some of the design elements that appear to be pockets aren't (the two flaps on top), and the bag really could use more real pockets and fewer faux ones.