Nobody wants to be labeled as what you're against, and yet non-believers keep being pigeonholed this way. ("Non-believers" is another good example.)
  1. Humanist
  2. Reasonist
  3. Scientist
    May be subject to brand confusion.
  4. Skeptic
    Not much better than atheist, though. We land on lots of things.
  5. Free Thinker
    A little too indulgent for my taste.
  6. Secular ?
    Suggested by @Zeealist