http://www.asmp.org - American Society of Media Photographers. Find a photographer.

http://www.nanpa.org - North American Nature Photography Association also promotes nature appreciation and environmental awareness.

http://www.nppa.org - National Press Photographers Association. Articles and resources on ethics, copyright, billing practices, and current issues.

http://www.photoshopuser.com - For members of the National Association of Photoshop Users (NAPP). Costs $99/year. Not so much an association as it is a magazine and excellent online reference.

http://www.ppa.com - Professional Photographers of America. Find a Photographer, business services, calendar of events, classifieds, vendors directory, press releases, chats, message boards.

http://www.psa-photo.org - The Photographic Society of America (PSA) is a 74 year old association of advanced amateur and professional photographers with over 5000 members in the US and 60 other countries. They have a week long conference each year, and publish a magazine, the PSA Journal.

http://www.rps.org - The Royal Photographic Society has history, classes, message boards, and articles.