I just picked up this bag in the clearance aisle of the outdoor section at my local Walmart for $25 (normally $50). When I got home and checked it out, I was shocked at all of the features this bag has to offer. In addition to adjustable shoulder straps and lots of other straps to hold gear on the outside of the bag, it has a built in rain cover! If you're in the market for a cheap weekend pack, this is a great value.
In store only. Brickseek link for availability:
Walmart link for reviews and product description: