SAF is a strong national org recommendation from me. SAF is the one suing many states and actually making headway to the USSC to overturn decades of increasing gun control laws. IIRC, SAF Life membership was $150. I have met Alan Gottlieb (Exec Dir of SAF) a couple of times and talked with him and his Wife (who had testified against gun control efforts by the UN at the UN as a NGO) at the GOAL Banquet 2 years ago. They are "real people" and doing real good work at re-establishing our 2nd A rights at a national level.
http://www.saf.org/
Support Comm2A if you are a MA resident, as they are doing similar things in MA courts (with assistance from SAF).
GOAL is the MA lobbyist group trying to make changes thru legislation (which is a much tougher row to hoe than most people understand).
NRA is the 800# gorilla in the room that everyone in DC hates/fears. They are the national lobbyist group. They have done some good things, but oftentimes compromise our rights away (e.g. Brady Bill, NICS, MG ban, etc.), so they tend to be very controversial amongst gun owners who believe that the 2nd A is about "self-defense" and NOT about hunting and bullseye shooting.
Disclaimer: My Wife & I are Life Members of: NRA, GOAL, SAF and Founding Members of PGNH.