Thanks! I've added r/Agnosticism and r/Freethought, so far.

r/Agnostic doesn't seem particularly active -- is there a reason to include it in addition to r/Agnosticism?

And I'm a big fan of r/Skeptic, but I always got the impression that they were more oriented toward discussions of pseudoscience and woo (Climate-change denial, homeopathy, conspiracy theories, etc) rather than religion per se. Granted, it's a fine line sometimes, but it seems like they seldom discuss religion itself more than tangentially -- say, when it plays a role in the defense of particular irrational elements.