Professional seed trade organizations may not be of interest to the average gardener, but they arose because of home gardeners. For example, the American Seed Trade Association was formed to protect American seedsmen against "fraudulant and unjust claims for damages," to fight for lower postage, and serve as a way for them to network. While most of these seed organizations don't have much information for the home gardener they may be of interest to you if you're researching seeds. Also, a couple of them have grants or scholarships if you're a student interested in the field. These website are NOT included in the Seed Snatcher search engine.
If there's a seed trade association you think I should list leave a message in the comments or contact me.