Pennsylvania Certified Organic
http://www.paorganic.org/
This accredited organic certifier publishes an annual list of the companies its aware of which sell organic seeds. 

 

Saving Our Seed Project
http://www.organicseedsourcing.com/
The Save Our Seed Project of the Carolina Farm Stewardship Association offers a comprehensive search of organic sources.

 

Washington State University
http://csanr.wsu.edu/Organic/OrganicSeed.htm
The Center for Sustaining Agriculture & Natural Resources at Washington State University produced a list of organic seeds by variety in January 2006.