Origami Groups
OrigamiUSA is the American national origami society. It offers origami resources via their website, magazines, online shop and conventions. Their website has a link to other origami groups, both in U.S. regional and international.
Portland Oregon Paper Shapers (POPS) is the local origami group that meets monthly in Portland and Tualatin. Please email OrigamiPDX@gmail.com in order to join POPS’ mailing list (Google group) and receive updates on the meeting schedule.
Origami Paper, Books & Kits
Many art/craft/paper supply stores, bookstores, and Asian gift shops carry origami papers, books, and kits. There are also many online stores that carry them. Most origami papers are made in Japan so you will find the largest variety and at the lowest prices in Japan. As far as origami papers that are purchasable in the United States, I like ones from MUJI, Toyo and Tuttle. As for origami books and kits, please find publication reviews on my Reviews page (here).