I have done the free hanging pocket as mentioned, but keep in mind if you put something heavy in it, it will drag the edge of the bag down.
What I usually do is run the handles all the way around the bag like this:
http://www.instructables.com/id/How-...bbing-Handles/
the straps hide the side seams where you have attached the pocket on the inside. You can also add a pocket to the outside. You don't have to make the handles go all the way around, just down far enough to cover the pocket seam. If you make the handle a contrasting fabric, it becomes a design element.