"The NRA" isn't one thing. As people have mentioned with the NRA-ILA, there's something like a half dozen NRA arms. ILA is the Institute for Legislative Action- I believe the lobbying arm, The NRA-PVF (Political Victory Fund- I think donations to candidates) and others I can't recall, but they all do different altruistic things- getting women involved in the sport, supporting college and high school teams, and so on.
The Second Amendment Foundation is similar to the ACLU with a firearms bent-primarily suing on behalf of clients over second amendment rights. I believe they did Moore v Madigan for example, that forced Illinois to join the other 49 states in enacting a concealed carry law.
The NSSF or National Shooting Sports Foundation is a trade lobby, and primarily works with/for the manufacturers.
There are other smaller ones, especially when you get to the fairly local level, like CalGuns, or a state association, but the NRA and SAF are the big two for us "hobbyists".
Edit to Add: I wouldn't be quick to rule out sending money to the Scholastic area, either. If more kids letter in trap, and go to college on a rifle shooting scholarship, etc. we get more shooters, and more people involved, emotionally invested in the right. It can only be estimated, but the current estimate is that only 1 in 3 people/households have a firearm. That number is shrinking over time.
