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.