http://www.adherents.com/lit/comics/comic_book_religion.html If you are a comic geek then you probably already know that Night Crawler is Catholic and Kitty Pryde is Jewish but what about The Hulk? Or over at the competition you can't miss that Azrael is Catholic but what about the new Green Arrow?
Like real people some comic book characters are very open about their religions and some aren't. For regular day to day interactions it probably doesn't make much of a difference but once in a while, like around holidays, or when you are facing supernatural evil, it's helpful to know their beliefs.
It's especially helpful if you plan on writing about any of them. A person's religion influences a lot more than where they are going to be Sunday morning.
This page features a handy table of characters and their religious affiliations sorted by religion. If you click on the religion listed it will take you to an article with the supporting documentation as well as some nice illustrations of the characters. Clicking on the religions listed at the top of the page takes you to the section of the table for that religion.
The sidebars are fun too. They have a list of characters who are current or former members of the clergy and a list of characters who are angels.
This is a work in progress and they welcome input from readers. The list is heavy on DC and Marvel characters but there are characters from other publishers, including manga, although there aren't that many manga characters. If a favorite character isn't on the list and you can make a case for a particular affiliation by all means feel free to email them with your information.