American Legion. I used to be an active member but had a falling out with a few guys. Now inactive but pay my dues. I hope the dues is going to help out with veterans affairs and not some lobby greasing senators/representatives.
VFW - Life member; we have nice chapter here that does a lot, even though there is a lot of "political crap" within its doors. I try to help, but time is hard.
DAV - Life member; because they help a lot of vets to get their just fruits when the VA Beauracracy is hell bent on taking it from them. They sure helped me. I donate a lot to them, and participate when I can.
American Legion; because when I first moved here they had the best organization in the area. They sold their building, and let politics get in the way of who they were. They're almost extinct now. I still belong as a member "a large".
Air Force Sergeants Association - Life member: Joined as a life member when I was still on active duty. Don't have a local chapter anywhere near me.
There are numerous others that I could join, but don't. If you join to many organizations, you end up with no life, and, a lousy member of most, if not all, of the organizations of which you are a member.