Hi Josh H.,
+1 for the Greater Seattle Aquarium Society (GSAS). ukigumo11 is correct, memberships are very inexpensive. Lot's of 'plantheads' in the clubs and the monthly auction at the end of most meetings has some rare plants really cheap. Our November meeting is our annual plant auction of plants, fish, shrimp, hardscape, but no equipment....last year almost 600 items sold in about 4 hours.
There are world class speakers on a regular basis like Tom Barr, Christel Kasselmann, Ian Fuller, Oliver Lucanus, Ad Konings, Dick Au, and others in the last several years.