I'm a member of both the NRA and SAF. Without getting into a NRA vs. GOA vs. anything else thread veer, suffice to say that I've not been impressed with GOA and, as such, haven't seen a necessity to join them.
SAF is the abbreviation for Second Amendment Foundation and they work almost exclusively on the judicial side of things. Both
Heller v. District of Columbia and
McDonald v. Chicago were SAF lawsuits.