Check out this article in the National Post by Lawrence Solomon, founder of The Green Beanery (www.greenbeanery.ca).
In a follow-up email with Lawrence, he said (in answer to my question “how do we know which coffee to choose?) “African farmers are almost all smallholders. If people select beans from, say, Burundi, Congo, Rwanda, and Tanzania, they’ll be supporting small farmers and also enjoying delicious coffee.”