Ruffwear Palisades Pack
Price Paid: $90
This pack is awesome. By far the best I have ever used, and would never again use any other brand. This pack holds two 1-liter water bladders (included), and has enough room to store a week's worth of food, plus a few treats.
The pack also has a daisy chain on the top/sides that I use to strap on a small blanket. The pack is removable from the harness, and is done easily with 4 snap buckles. Both the pack and the harness are extremely well made, and are very durable.
Measure your dog before you order. I ordered a medium at first and it was WAY too large for my Siberian Husky. I returned for a small and it fits great and has plenty of room left for when she fills out the rest of the way (she is 8 months atm).
I highly recommend this pack!