A meta-list of resource links compiled by the USDA (May 2011)
Medline (a service of the US National Library of Medicine/NIH) list of herbal supplements with summaries of known use, effectiveness and risk.
FDA consumer updates on dietary supplements http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm153239.htm
The University of Maryland Medical Center Alternative Medicine Index
"Herbal supplements: What to know before you buy" from the Mayo Clinic