Someone recently found this blog by googling “how many asexuals are atheist.” I don’t know, but based on unscientific impressions, it seems like a lot.
Also, for what it’s worth, the 2008 AVEN survey found 53.8% of their respondents to be nonreligious, but you should take that with a grain of salt since AVEN can’t be expected to be able to draw a random sample of the asexual population (they’re constrained to anglophones, for one thing, and not everyone who answered the survey identifies as asexual, etc.).
So, again: I don’t know.
If you’re looking for some kind of causal correlation (the way people sometimes try to do with asexuality and autism), I doubt you’ll find one.
If you’re looking for fellow atheist aces, then… well, there are some who follow this blog (say hi?). Walk into any ace space online or off, I bet you’ll find a few.