Henriette's Herbal Homepage -- On her plain but well organized site, Henriette Kress has great files, archives and articles onsite and mirror links to many others. An awesome search engine onsite that searches her own extensive herbal files, as well as much data from Michael Moore's Southwest School of Botanical Medicine. http://www.ibiblio.org/herbmed/index.html
Southwest School of Botanical Medicine -- The homepage of author Michael Moore, one of the first herbalists to write extensively on the Medicinal Plants of Western North America. On this site he has numerous useful articles relating to his herbal school as well as old herbal medical manuals and articles stored as adobe acrobat files. http://www.swsbm.com/HOMEPAGE/HomePage.html
Medherb.Com -- The homepage for Medical Herbalism magazine, published by herbalist Paul Bergner. Another absolutely awesome site that offers access to a wide range of offsite resources in a well-organized topical format. http://medherb.com/
Herbal Hall -- Lots of good information as well as connections to herbal chat lines. Beware though, the site often seems to be under construction and not fully functional. http://www.herb.com/
Health World's Herbal Materia Medica --Plant Monographs by herbalist David Hoffman. Part of a larger alternative health and shopping site. I haven't looked through the whole site but there appears to be a whole lot of information on a great many subjects here. http://www.healthy.net/clinic/therapy/herbal/herbic/herbs/index.asp