The comments at "Hang With Friends" have had a few church signs recently:
Supposedly they're all real ...
There are some extremely well-done fake church sign generators at says-it.com. Think high-quality automated photoshopping, complete with a variety of fonts, logos, and even reflections on the glass over the changeable message.
Loren Miller told us about them, with some funny examples by him and others, at "Do-It-Yourself Church Signs!"