Here are some at Kiwi Magazine.
Coupons.com They currently have coupons for Nature's Bounty, Good Earth Coffee, Muir Glen & Cascadian Farms
Mambo Sprouts has a variety of printable coupons, plus you may find the paper booklets at your favorite natural foods grocery store or section.
Brown Cow Farms
A Variety of Online Retailers of Natural/Organic Products
Nature's Path & Organic Valley (plus promotion details)
Hodgson Mill (but online with their own sales & specials)