This is a very good question and one that is hard to answer.
Many excellent practiced herbalists exist, but they aren't into writing about it. Some are into a more clinical approach and more academic (hence research), and some are the occasional herbalists or personal ones. None should be discounted. They all have their importance.
We do have the American Herbalists Guild you could look up and find books through them and also names of herbalists. This is a very expensive (I belonged for a few years) group and not all herbalists belong to this group. I've been to their symposiums and they were fantastic. But very spendy. Just because an herbalist doesn't belong, doesn't mean they aren't any good.
American Herbalists Guild | An Association of Herbal Practitioners
Another group is the American Botonical Council.
American Botanical Council: Homepage
Again, this is an expensive group. Just like anything else, not all good herbalists belong, nor are all herbalists good. This site is more "academic" or "clinical" in nature.
Then you have even more!
You can look some herbs up on the phytochemical database:
Phytochemical and Ethnobotanical Databases
Also you can look up the phytochemicals and learn what they do. But herbs aren't always what they appear via chemical breakdown. Some of us believe they are complex in the way they work and plants actually have "lives" so how can you define this? You can't. So then you have what is called "case histories" Case histories are experiences of herbalists and their clients and how the herb worked. Each step was documented. The way herbs work often do not fit into a nice neat package of science. Hence the reason so many studies on them are not acceptable nor realistic.
THen you have the National Center for Complementary and Alternative Medicine:
National Center for Complementary and Alternative Medicine [NCCAM] - nccam.nih.gov Home Page
Then you have other areas of discipline:
The American Herb Association
Michael Moore - SW School of Botanical Medicine Home Page
Herbal Education -- Beginning, Advanced, Clinical, Classroom, Distance
Welcome. | Henriette's Herbal Homepage
David Winston, Herbalist AHG
Herbal Constituents
All Things Herbal: Heartsong Farm Healing Herbs
Herbal Medicine and Spirit Healing the Wise Woman Way - Susun Weed - Complementary Integrative Health Resources for Women
This herbalist, I've been to his talks and he's really there regarding mushrooms.
Christopher Hobbs - The Virtual Herbal
Many sites are blogs of herbalists who are practicing and may not "belong" to any group, and may not publish big thick books, but they are excellent all the same!
HerbNET - The Most Comprehensive Site for All Things Herbal
This person, Jim McDonald, started out self taught. I've watched him over the years and he's quite impressive! Check through his site and remind yourself that you too can learn, you just have to really do a lot of research and listen to a lot of herbalists.
michigan herbalist jim mcdonald ~www.herbcraft.org~ herb classes, weed walks and other herbal opportunities...
Gosh i couldn't even begin to list them all.
I really like Isla Burgess if you ever want to go study!! I went to some of her talks at symposiums:
About The Faculty of Herb College Providing Herbal Studies
I saw that many herbalists were getting certified so I decided to follow suite and began here:
American College of Healthcare Sciences - Formerly Australasian College
That was a personal decision for me. Not everyone needs to get "certified" but if you are practicing or creating products, it comes in handy because you learn many of the laws and about insurance, and so many other things. I wanted some structure for this.
Also, check into the history of "Herbal Practice" it is very interesting. Since the beginning of time herbalist or physicians practicing herbalism have fallen under extreme scrutiny. Early on actual "disciplines" regarding this cropped up such as Eclectic, Thomsonians, and more. Tensions actually rose between groups. Its a very interesting history. Just a start on the history is written here, but so much more to it!
Chanchal Cabrera MSc, MNIMH, AHG | Medicinal Herbalist
This should help steer you in a direction. Like I said, it is not written in stone. This is not like pharmaceuticals or physicians where everything is followed a certain way.
You will find a LOT of variations. It is not a science yet in some ways it is. But if you depend just on science, then you are missing out on actual practice and understanding of herbs.
Wnderingherb