...for seeds! I just added four of my favorite seed-sellers to the links list. They all have interesting websites and/or catalogs you might find useful and/or enjoyable.
(They're all in California, except for Territorial which is in Oregon.)
J.L. Hudson, Seedsman: I keep this groovy old-school catalog in the drawer of my nightstand. He also sells gibberellic acid kits.
Peaceful Valley Farm & Garden Supply: I did my soil test with these folks.
Swallowtail Garden Seeds: Great website with lots of pictures; they sell some hard-to-find seeds too.
Territorial Seed Company: I ordered most of my vegetable seeds from them.
Two links I've had up for awhile:
Seedhunt: This woman works at Suncrest Nursery (wholesalers) in Watsonville and runs her own seed business. She sells rare CA natives and exciting restios, among other things.
Theodore Payne Foundation: Dedicated to preserving and disseminating CA natives and wildflowers.
Please feel free to list some of your favorite seed sources in the comments.