The herbal I turn to the most is Rosemary Gladstar's Herbal Recipes for Vibrant Health. This book covers a wide variety of gentle herbs and also gives detailed instructions for making herbal products. It's a good book for beginners but also has information which can be helpful to those who are more experienced.
Susun Weed is one of the herbalists I respect most and I believe her 7 Rivers of Healing system is a brilliant and practical method for choosing the right care for yourself and your family. (You don't have to take her course to benefit from the outline on that page.) I have found all of Susun Weed's books to be helpful but I believe her most helpful books are Breast Cancer? Breast Health! The Wise Woman Way and Down There---Sexual and Reproductive Health The Wise Woman Way. Breast Cancer? Breast Health! is a compassionate and informative book which educates women on self care and guides those with breast cancer through the many choices available. Down There is an encyclopedia of reproductive health and is a gold mine of information. It is practical and tasteful but may not be for the squeamish. Susun Weed also has a wealth of information on her website, including an active forum.
Herb Mentor is a rich community of herbalists with podcasts, articles and a forum available to members. You get a lot for a only a small monthly fee. I am always learning something new there. (Disclosure: I am an affiliate of Learning Herbs/Herb Mentor and receive a commission for referrals through the Learning Herbs ad on my blog.)
Green Deane has an unbelievably thorough wild edibles website with hundreds of videos and articles.
Henriette's Herbal is a scholarly website with lots of articles and resources for herbal research.
For smaller quantities of herbs, Jean's Greens is a reputable herb shop with quality products for reasonable prices.
Last but not least, Mountain Rose Herbs is a bulk herb company with a solid reputation in the herbal community. I appreciate their reasonable prices and quality products. (Disclosure: I am an affiliate of Mountain Rose Herbs and receive a commission when you order through the link below.)