Becoming Orgasmic by Julia R. Heiman, Leslie Lo Piccolo, Joseph Lopiccolo, published by Piatkus Books (1988) [Buy]
A sexual and personal growth program for women.
ISBN 0861887980

Clitical
A good web site about female sexuality, including anatomy (with pictures), female masturbation, sex toy reviews, and other sex topics
http://www.clitical.com/

Dick: A User’s Guide by Michele C. Moore and Caroline de Costa, published by Marlowe & Company [Buy]
Written for men and women of all ages, two doctors demystify the penis with a wide range of education about anatomy and function along with advice on safe handling and proper maintenance.
ISBN 1569244294

Erection Photos
Penis photos (non-sexual), flacid and erect, with information on size and shape. Good information for clients who have penis size questions or issues.
http://www.erectionphotos.com

Femalia by Joani Blank [Buy]
A collection of thirty-two excellent-quality color photographs, both to celebrate the beauty of these often-hidden parts, and to provide women with references to help them answer their own questions.
ISBN 0940208156

The Multi-Orgasmic Couple: Sexual Secrets Every Couple Should Know by Mantak Chia, Maneewan Chia, Douglas Abrams and Rachel Carlton Abrams, published by HarperOne [Buy]
This book contains a series of exercises rooted in the Taoist sexuality tradition to help couples to learn a deeper sensitivity to their individual sexual energy and how to cultivate the flow of sexual energy between each other.
ISBN 0062516140

The Multi-Orgasmic Man: Sexual Secrets Every Man Should Know by Mantak Chia [Buy]
We refer people to this book as a resource for shortening the period between ejaculations. It has helped many men.
ISBN 0062513362

The Multi-Orgasmic Woman: Sexual Secrets Every Woman Should Know by Mantak Chia and Rachel Carlton Abrams, published by Rodale Books [Buy]
The authors combine their knowledge of Taoist sexuality tradition and Western medical research in a program of exercises designed to teach women to increase the length, intensity, and number of their orgasms.
ISBN 1594864853

The-Clitoris.com
A site dedicated to women’s sexual pleasure and health, with an emphasis on pleasure anatomy.
http://the-clitoris.com/