Canterbury Atheist points out that the world’s top ten peaceful nations on the 2010 Global Peace Index are among the world’s least religious nations. CORRECTION: I should have written, among the world’s top ten peaceful nations are a high percentage of the world’s least religious countries, measured in terms of personal religiosity metrics (like reports that “religion is very important in daily life” and church attendance statistics, see the comments below this post for documentation).
Here they are (with their 2009 ranking):
New Zealand (1 in 2009)
And the bottom ten (and their 2009 ranking) are: