this message is for toni - i can't speak to the economics of grinding your own flour. it's just an educated assumption that it would be cheaper, unquestionably healthier (store grains in the freezer).
as far as places to buy bulk grain you can usually find a good health food store or co-op somewhere near you in the real world. i have a bunch of bookmarks if you prefer to shop in cyberspace: bobsredmill.com, beanegrains.com, kingarthurflour.com, healthy-eating.com and brownsville mills (http://www.skyport.com/brownvillemills/index.html)
that should keep you busy for a while. :)