Charles,
Any type of weight is fine for hanging - everything from weight plates (the kind found in a gym) to a jug of water has been used.
Personally, I prefer the weight plate approach because it offers a very accurate method of measuring the force I am using - add a pound, remove a pound. You get the idea.
Check out this thread for a number of simple ideas on how to employ weights in your hanging routine:
Basic Weight Plate Post
Here is an image of a typical assortment of weights. Purchase them at any Sports Authority or other sports supply type joint. You only need 25lbs at most - so don’t go crazy, unless you expect to run for Governor of California someday: