I've begun organizing quotations by Karl Marx on religion, accompanied by sources and web links, as well as a listing of the major English-language anthologies on the subject:
Karl Marx on Religion: Sources & Quotations
I will add to this compilation as I examine more quotes. I will probably add a listing of relevant writings by Friedrich Engels and possibly quotes as well. I will move on to organize the various quotations on this blog into pages on my web site. Also, I will begin to compile a working bibliography of important works by and about Marxists on religion and atheism.