Here are some images of the Tenba Mini Messenger Laptop/Camera bag.
I can take a good amount of gear in this bag and it would be fine for a day trip, but for distant travel with photography in mind, there are more lenses I may want to have along, in addition to travel snacks, Passport, travel papers, wallet, cell phone, book, map, water bottle, yada, yada that would way more than max this bag out - for my needs. I plan to also get the next size up, the "Small" Tenba Messenger Bag and for travel, split the gear between the Mini and the Small - my wife with the Mini and I with the Small.
Shown with iPad in the case, but this will also hold a MacBook Pro 13" as well.
Accessory Bag sitting on end in the center: