Here's a new entry to the discussion, from an atheist's blog on Patheos, that actively advocates for a secular Christian identity that would mirror that of the secular Jewish community (Judaism is particularly welcoming of its nonbelievers).
Consider what this might be like. A secular Christian—I could be a candidate, for example—might go to church for the beautiful or traditional or inspiring music. The church building might be a draw, whether it were awe-inspiring or quaint. Sermons about finding the right path or avoiding the shallow temptations in life or even Bible stories might be edifying. Services could mark the important events in life such as births, marriages, and deaths. Whether the secular Christian went weekly or only a few times a year, the community of good people, eager to help others, would be welcoming. It might give focus to good works, providing opportunities for volunteering and direction for charitable giving.
But—and here’s the interesting bit—secular Christians would reject the supernatural origin of Christianity, would be open about their atheism, and would be accepted within the church community. The Christian church has millions of members who are secular Christians except for the last bit. They’ve lost their faith in the supernatural claims, they’ve admitted this to themselves, but they can’t come out to their church community. The concept of a secular Christian would allow these people to keep their community, charitable, and even family connections.
The Christian church isn’t pleased with these ex-Christians simply leaving the church, and this broadening of the church community, as is done in many Jewish communities, could provide a soft landing for many mainstream churches hurting for members. Conservatives will insist that a no-compromise position be taken, but the church is determined to evolve, and this direction seems to be a win-win.
Speaking of her own experience as a non-believer who attends church:
I'm a non-believing member of an Episcopal Parish. Indeed, I'm technically "legal" as a member: As a child, I was baptised and confirmed Roman Catholic. I had a good religious education (Catholic school through 8th grade). Now, as an adult, I not only attend services but donate time and treasure to the Episcopal Church.
Probably the main difference between me and other people who might fit this description is that I'm not in the closet about my lack of belief (although I admit I'm hesitant about telling people I don't know well, in case they take it the wrong way or think I'm being disrespectful, which I am at pains to avoid). I don't take Communion, and while I enjoy the service, generally I don't say the words or sing the hymns.
Is there a place for people who are "culturally Christian" in church?