I use a Timbuk2 Spire bag (
http://www.timbuk2.com/spire-macbook-laptop-backpack/306-3-1...). It's water resistant has two outside zipper pockets and a large inside pocket with a laptop sleeve, plus a small zipper pocket inside too. I usually throw a small zipper bag inside that holds all my cables and dongles, but the outside front pocket would work just fine. It has lots of webbing on the front and side which are great to attach things via a carabinier- I usually have a baseball hat and fold-up reusable grocery bag on mine. I also love that the material and back padding give it structure so it won't flop on the ground like a Jansport from high school.
I cowork and often bike around with my stuff and it has a padded, breathable back and a sternum strap which helps it stay in place for short commutes. It also has an easy access mess side pocket that I store a water bottle in.
I usually take it out of the house with me 4-6 days a week and it's held up like a champ for over a year carrying two laptops most days. It is a bit on the large side, but when not full it's pretty slim.
If it's not to your style, check out their other bags, I've never met someone who didn't love their purchase there.