Free Plants By Mail (freeplantsbymail.org) was started by local growers as a way to use the surplus plants from nurseries and also as a way to support The Nature Conservancy. Free Plants By Mail offers a new free plant each month. This month they are offering Dieffenbachia. Although the plant itself is free, you do have to pay a small shipping and handling fee of $6.95.
This organization also has over 100 plants available for sale on their site. 100% of the proceeds from the sale will go to The Nature Conservancy.