Origami USA is a great organization that I've been a part of since the 1980's. Membership gets you a quarterly publication of origami news and diagrams called The Paper. You can also order books and paper from the Origami Source at a 10% discount. Back when I first joined OUSA, the group was still known as The Friends of the Origami Center of America, and The Friends' list of books was a great way for me to get new titles from the States and overseas.
The other "fringe" benefit of membership in OUSA is the annual convention held every year in New York City. It's a great way to meet other people who understand what it is you do with those bits of paper that you fold. The convention also gives you a chance to see and learn plenty of new, and many times unpublished, models.
For more information on joining OUSA, contact them at:
Origami USA also has a web site with more information: