<p>Well first off, avoid ALL schools that have any religious affiliations :-).</p>
<p>I second willmingtonwave's comments about Reed and NYU. Also try looking at Vassar, Swarthmore (although there is a religious presence because the school has Quaker roots), Bard, Hampshire, Brown, Sarah Lawrence... basically any school that has a "liberal" reputation. I agree that you might want to stay away from the South and Midwest, however, there are "Atheist Alliances" at a variety of southern/midwestern colleges including the College of Charleston and the University of Illinois. I imagine (and hope) that at most schools (as long as they're not religiously affiliated) atheism is a perfectly normal aspect of the community.</p>