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
Post Office In Paradise has a wealth of information for anyone who has an interest in Hawaii philately.