The Whole Dog Journal, a holistic nutrition and training newsletter has had several articles on black salves. They sound a bit scary but effective, I would definately read up on it before using them. They have also run an interesting article about the anti-cancer properties of unrefined virgin coconut oil. If you go to their website you can search back articles for information.
I highly recommend this natural dog care magazine. They accept no advertising. They are long time proponents of the BARF diet and positive training.
Whole Dog Journal is the monthly guide to natural dog care and training.