Here's a list of the 20 least religious countries (article) in the world. This is from an encyclopedia chapter summarizing survey data from various countries. Obviously the quality of surveys varies widely across countries, so the author, Phil Zuckerman of Claremont College, gives ranges for each country.
1. Sweden (up to 85% non-believer, atheist, agnostic)
6. Czech Republic
9. South Korea
10. Estonia (up to 49% non-believer, atheist, agnostic)
20. Canada (up to 30% non-believer, atheist, agnostic)
The big surprises for me is South Korea... I have heard about the Christian revival there & has assumed that the whole society was much more religious and Isreal... for obvious reasons.