I like Coastal Classic products, because they're so non-toxic, but their foundations simply do not cover anything.

This was the very first natural foundation I tried, and I was NOT pleased with the results. I purchased the sample size of the "Ivory Wheat" foundation, along with the base primer. The powder ended up being too dark for my very fair yellow toned skin, and gave absolutely ZERO coverage. :( It applied very unevenly and look extremely cakey. I ended up washing it off right away. While mineral makeup in general doesn't give me enough coverage, I found Alima Pure mineral foundation to be far superior.
However, I have been very pleased with the facial care products I have purchased from Coastal Classic Creations, and their customer service is fantastic. If you want to try out their makeup, they offer really neat trial size bags where you can mix and match what you want (I ended up purchasing the "Coastline Makeup Bag".
***After trying countless natural/organic foundations, I have FINALLY concluded that Gabriel Cosmetics works the best for me. The combination of their Liquid Foundation and Dual Powder gives wonderful coverage without causing greasiness or breakouts!*** :)
Hope this review helps!
EDIT: 10/10/12: After trying Kat Von D's new Lock-It Tattoo Foundation, I am in love!!!! PHENOMENAL coverage without oxidation/greasiness. See my review on this for more details, if you're interested. Not super natural, but at least the formulation is without parabens, mineral oil, fragrance, etc. :)