There is an internet site that gives church attendance stats for different areas and is also broken down by religion/denomination. It was posted here about a week or 2 ago... very interesting and sometimes surprising. Forgot the link, but you might be able to search for it.
I wasn't able to find it but a search on google found the following which is very interesting:
American Religious Identification Survey
It contains the following table. It doesn't list who goes to church on a weekly basis, but I think puts to rest the argument that 2/3s of Republicans do and only 1/3 of Democrats: