M.S.D.A. Capitol Stamp Gallery is a member of the Minnesota Stamp Dealers Association. The M.S.D.A. web site has links to other dealers in the Midwest, and has a listing of upcoming stamp shows and events in the Minnesota area.
A.P.S. A visit to the American Philatelic Society is a must for every serious collector.
A.R.A. The American Revenue Association
The Museum of United States Essays & Proofs Proofs undoubtedly display the engravers' artwork at it's best. To view some very impressive images, and to learn more about the background history of these beauties one should visit this impressive site.
Post Office In Paradise has a wealth of information for anyone who has an interest in Hawaii philately.