Think Tank Shape Shifter Backpack - Digital Photography Gear
Think Tank makes what I think is a great backpack for taking key gear and your laptop with you. It is built well, fits a ton of stuff and feels great on your back.
Some of the larger back packs are just way to big and feel very top heavy on your back. This bag is comfortable and distributes the weight very well with the built in hip-strps.
The only downside to this bag along with almost all shoulder bags is that its not fast to shoot out of. You have to put the bag down, unzip it, pull the lens out you want to use, put the other lens back in the bag. But it is great for getting your stuff from point a to point b comfortable and safely.