I just finished a very interesting book called "Trick or Treatment," which claims to summarize the scientific research into the effectiveness of alternative treatments, particularly chiropractic, homeopathy, acupuncture, and herbal medicine.
http://www.amazon.com/Trick-Treatment-Undeniable-Alternative-Medicine/dp/0393066614/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1220545415&sr=8-1Although the authors are very conservative and overly confident of the "objectivity" of the scientific method (one of the authors is a physicist), they don't reject alternative treatments out of hand, but try to apply the rigors of clinical trials to judge the effectiveness of the methods under scrutiny.
I found the discussion of the philosophical underpinnings of chiropractic and homeopathy to be particularly enlightening.
The authors (one of which used to be a homeopath) argue that homeopathy is no more effective than placebo, and that homeopathic remedies contain not a single molecule of an effective ingredient. The concept that these remedies have "memory" of substances seems pretty far-fetched to me.
Herbs definitely contain active biological agents, and the authors note this and defend herbal therapy.
