You get a subscription to a magazine, for one. I get American Rifleman
. Once I've read it, I remove my name and address and either give it to a friend, or leave it somewhere for others to find. That's my combined recycling & spreading-the-word program.
The NRA (& the NRA-ILA) are also the 800-lb gorilla of gun law. There are some other very good organizations (Second Amendment Foundation comes to mind), but I don't think any of them is as large as the NRA.