I have several water brothers. I was quite excited when I first heard there was a “real” CAW. Then I read about them.
Color me underwhelmed. RAH would vomit. While I believe that he was at least passingly familiar with Paganism and “other” religions, I think the PC Hippie Love fest that CAW is would revolt him.
Thou art God, no thou art Goddess, because the devine is without gender. It just IS. God is that which groks.
I’ve thought of taking a stab at it myself, but I’m just to dang lazy.
Say, I don’t think anyone’s mentioned the Great God Klono from E.E. “Doc” Smith’s Lensmen series.
I think Roger Zelazny’s books had more of the “God stuff” in them than anyone else’s, but rather than invest them in religious trappings, he dealt with his supernatural characters as regular people, so a lot of people missed it.
Also, he may have been far too good a writer for religion. Real-world groups rarely spring up around the best writers. Frex, L. Ron. But also frex, John Norman, who has attracted a large group of people who lead the “Gorean lifestyle.” Although not a religion, it’s definitely a subculture. (To be fair, Norman never tried to build up the Gorean lifestylers and to a certain extent discouraged them, they just sprang up anyway.)
The religion in A Canticle for Leibowitz is straightforward Catholicism.
That’s one of the many things that never made sense in the half-baked universe of Star Wars: why is it a religion? The Force is easily demonstrable as real, and apparently understood on a scientific basis (those midichlorian thingies); so why muddy the field with mystical stuff?
James Blish wrote some religious stuff, but if I recall that was from a Catholic basis. How about L. Sprague de Camp?
This Year’s Model, Stranger On A Train, you both seem to be saying the same thing. 
Baldwin: I think the religious part of it can be explained by stating that the intense train necessary to use the force requires religious-like training. Or course, the jedi could just start boot-camp like training ground intended to create more jedi, rather then monasteries, but they just want to hold on to their powerbase. 
Warren Ellis certainly has a way with religion. His City in **Transmetropolitan ** generates a new religion every hour.
James Blish wrote a Case of Conscience (and, I think, some other stuff I haven’t read), but it was straight (if futuristic) Catholicism. There’s a lot of SF with religion, but most of it doesn’t meet the requirements of the OP. Just mentioning religioon or including a religion doesn’t seem to be the same as creating an SF religion that then gets picked up.
There are a lot of “created” sf religions, too, that never got adopted in the Real World – Heinlein mentioned Martian religion that differs from SiaSL in Between Planets, Larry Niven/Jerry Pournelle mentioned a made-up religion in Inferno, and so on. I’d forgotten The Church of All Worlds when I first posted but that’s about the only real world case.
There have been cases of movements inspired by science fiction or philosophical works. Edward Bellamy’s Looking Backwards hoped to inspire more egalitarianism. There was some book in the late 19th/early 20th century that I read of in The Science Fiction Encyclopedia that had a lot of “subscribers” (including George Bernard Shaw), but it’s virtually forgotten today. I can’t help but think that Van Vogt and others weren’t hoping to spread the “gospel” of Alfred Korzybski (and who, interestingly, Hubbard seems to hacve borrowed from. Hubbard used to have hours-long transcontinental long distance calls with Van Vogt, back in the 1950s when that was neither common nor cheap.). Heinlein, in his recently-published first novel, Us, the Living, seems to be pushing that odd economic theory.
If you read David Weber’s Honor Harrington series of books, they have a number of different religions he uses (most of them are based on Christianity, though there are passing references to stuff like Shintoism and Judaism. The title character is, IIRC, a Third Reformation Catholic.
However, the only religion that he ever goes into any detail in is the Church of Humanity Unchained, founded by Austin Grayson, the leader of a group of Christian Conservatives who colonized the planet Grayson (and later, the planet Masada) as a means of getting away from all the corrupt members of humanity. Basically, they have the misfortune to land on a planet that, while it looks like a lush forest paradise, turns out to contain high amounts of radioactive material, and indeed, almost every native plant and life form is poisonous to humans. Somehow, they manage to carve just enough of a niche to survive and expand for 500 years before being rediscovered by civilization, and eventually their religion goes on to talk about God the Tester, and how every hardship is a Test to give you a chance to prove yourself worthy of being one of God’s people. Due to the 3 to 1 female to male infancy survival rate, and the all around abysmal infant mortality rate, they also adopt a form of polygamy, with each man being allowed to take up to 3 wives, with careful records kept to avoid any icky incest.
I always thought that would make an interesting religion. A Christian religion far more conservative than most others out there, but with polygamy. And a near-fanatical love of baseball (when the books take place, Grayson is one of 9 civilized planets in the galaxy that still plays the archaic and hard to understand game, including Earth, a planet which nobody seems to like anyways)
:dubious: Stranger On A Train seems to be saying that the religion in A Canticle for Leibowitz is a fictional, made-up religion. It is not.