OnColoring.com has coloring pages focused on a variety of religions and spiritualities such as Hinduism, Buddhism and Mandala. Christianity- and Judaism-themed coloring pages are available online at Coloring.ws. and at TwistyNoodle.com. Islam-themed coloring pages are available for free at IslamicPlayground.com.
Twisty Noodle provides a large collection of coloring pages based on concepts found in Christianity and Judaism such as angels, Bar Mitzvahs, dreidels and crosses. ColoringPages.net is another good resource for Bible-based coloring pages, offering printable sheets depicting Jesus, Noah and a number of other biblical figures and objects. Islamic Playground contains coloring pages filled with mosques, prayer mats and other Islamic images.