I mostly post on AR15.com. I see The Firing Line is closing down at the end of the year. That's too bad, I only recently found that one and it seemed nice.
I like Full-Auto.com, it has been a little rough previously (guys who were banned elsewhere went there and were annoying) but Tim (the owner) is trying to refocus the board more towards firearms so it's getting better and he's a good guy. I haven't posted here a lot, but it's another place I lurk occaissionally.
I don't know how those guys who are on 4 or 5 boards all the time due it!
Those are interesting sites you posted Mark, I don't think I've seen them before.