There is a good source of herbal research at drugs.com of all places, but to get at the good stuff you have to go through the back door. For example sage-
weblink:www.drugs.com/npp/sage.html
Substitute sage with the herb of interest.
It shows all the research etc.
Wiki also has some good info on herbs.
If you look under Herbalism, scroll down and there is a list of many herbs with lots of info.
weblink:en.wikipedia.org/wiki/Herbalism
Also Michael Tierra has some good books on herbs and healing in general. He also has some good courses on herbology.
weblink:www.planetherbs.com/
This site has a very handy drug interaction page, and lots of herb information and some other useful stuff.
weblink:www.umm.edu/altmed/