American Numismatic Association (ANA)
http://www.money.org

Pacific Northwest Numismatic Association (PNNA)
http://www.pnna.org
The PNNA site includes a list of other local (non-Boeing) coin clubs, a local coin show calendar (including regional convention information), local news and lots of additional information!

Also see the PNNA links page for an extensive list of other numismatic sites on the Internet.