Girls, myself, and religion apparently can't mix

The girl I dated for 2 and a half years was a staunch atheist, where I am a staunch Christian (though not necessarily prudish and strict, I do believe strongly in God and Jesus.) She was pretty awesome, and when we broke up I joked with her about how she'd have to turn lesbian to find another atheist-vegetarian since there aren't many guys out there like that.

With the Mormon girl, you just had crappy luck there, pal. Most Mormons are taught that "you marry who you date" and so dating outside of the religion is strongly discouraged (though not forbidden.)
The Christian girls could be the same way. Despite my being strongly religious, a girl I was interested in - who was also interested in me - refused to date me because I was not a "true Christian" in her MOTHER'S mind. Yes, this girl was over 18 too. Pfft.

While religion has never really been a factor for me in my relationships, having hooked up with an atheist, an agnostic, a new age spiritualist, a Mormon, a former polygamist, and a couple of Christians... I do however understand how it is so important to them in a relationship.

It's not that they think you're evil in any way. It's simply that a lot of Christian families are brought up to believe that if you are not Christian, you are going to hell. Not because you're evil, but because you "choose" to be "ignorant" of the "truth of God" so to speak. Many religious people view things in terms of the eternal perspective - so why get involved with a guy who is going to hell, when you could have someone who's going to heaven instead?
Another problem is all the pressure and (one might call it brainwashing) that a lot of Christians (especially girls) go through. Such as the example with the girl who was interested in me but wouldn't date me because of her mother's beliefs. A lot of the time, if their peers find out they're dating non-religious guys, they get all kinds of dirty looks and negative reactions from people, ranging in severity from mild to extreme. I've actually seen this one in action, and it's not pretty. Almost anyone would break down from that kind of pressure.

I wouldn't necessarily blame religion for all of this, by the way, just the stupidity of people.

Anyway, my advice to you would be about the same as Greykin's. One interesting way you could break into the religious topic REALLY quickly without worrying about awkwardness is to display a cross - either on your neck, or in your car, etc... I have one in my car - and inevitably she will go "oh, are you religious?" at some point during your first interactions. You can then say "no, not at all, I just like how it looks. Are you?" At that very moment, you can tell by her reaction if it's going to be a problem. If she starts lecturing you on wearing a cross when you're not religious, kick her to the curb If she goes "oh..." and gets all quiet, you'll probably need to abandon that one, too. If she seems interested in at least hearing WHY you think it's cool looking, that's a good sign. And if she laughs and says "me neither, that's kinda funny you have a cross though, you weirdo" then you're good.

How ya doing, buddy?