The Southern Forest Products Association (SFPA) is kind of like a customer service department for Southern Pine. They provide assistance to end users in understanding Southern Pine grading rules and design values while also marketing lumber products. The SFPA website at http://www.southernpine.com/ provides information for end users regarding green building, pressure treatment, and product applications in addition to providing span tables for joists, rafters, headers and beams.
The SFPA is closely involved with the Southern Pine Inspection Bureau's (SPIB) proposal of new Southern Pine design values. While SFPA is not directly involved with testing of lumber or the establishment of design values, they will be the group that helps end users understand and adapt to any changes in Southern Pine use. The SFPA has published a sample span table for joists and rafters based on the proposed design values. You can find the tables here.