"Safe" churches, Bob?
Well, I've always found Unitarian and Reform/Conservative Jewish and Congregationalist (United Church of Christ) services to be delightful. Most United Methodist churches on the West Coast are nice, but not the East Coast. Most Lutheran churches, but not the Missouri Synod (although I have been to wonderful Missouri Synod churches). Episcopalian churches are usually quite nice, but some are overly formal and some are angry about the nationwide Episcopal Church accepting gays and women priests. Presbyterians are a mixed bag - many tend toward the born-again side, but some are very open and intellectually stimulating. Some Baptist churches defy the born-again stereotype and are absolutely wonderful (and have music to die for). Most Black churches are very welcoming, and have amazing music and legendarily musical sermons (the Pentecostals can be a bit much, however).

There is usually at least one Catholic church in every diocese that is the "liberal parish," and a number of others that can be quite nice - stay away from Catholic churches that have anti-abortion propaganda displayed, because it's a sure sign that anger is a dominant aspect of their agenda. Catholic Churches run by religious orders, especially Jesuits and Franciscans and Capuchins, tend to be very open - but there are some religious (dis)orders that are horribly doctrinaire. I'm a bit hesitant to invite people to my own parish, because I think of it as a "work in progress." My pastor and I have our disagreements, but I have to say that he does a wonderful job in contact with the public, especially at weddings, baptisms, and funerals. I am an Associate Member of the local province of the Sisters of Mercy, a wonderful group of Irish-born nuns - and I'm proud to invite anyone to activities at their convent. For the most part, they are brilliant women with a passion for social justice (Glenn Beck wouldn't like them). My (Cork-born) pastor had Jimmy Crowley perform at the Mercy convent a year or two ago, and it was wonderful to have great Irish music with all those earthy Irish women there.

I've never been to a Quaker meeting, but I've been to lectures and song gatherings and a Quaker music camp that are very folkie-friendly.

Orthodox Jews can be a mixed bag, too - but I've had a wonderful time associating with Orthodox Jews, and I can't get used to the female rabbis and cantors in Reform congregations.

Tootler mentioned doing recorder performances in churches. There's an annual Twelfth Night recorder performance in an old Lutheran church in Sacramento, and it's just perfect; as are the performances of a cappella Christmas music in the Catholic cathedral and the Franciscan church in Sacramento. I can't imagine them anywhere else. We have the advantage of having at least one Chanticleer concert a year. I would imagine that most of the members of Chanticleer must be gay, but somehow they have no problem finding old Catholic churches to perform in. For most of my lifetime, the Catholic Church had an unofficial "don't ask, don't tell" policy about gays, but conservative forces have lately forced the Catholic Church to tighten up on that and a number of other issues. Still, most Catholic parishes don't go out of their way to be offensive about gays and abortion and other things. If you don't make an issue of it, they won't.

I guess I wouldn't have too many qualms about attending most concerts in churches, but I've found that born-again churches have a hard time resisting the temptation to proselytize (and pass the collection plate) during performances. Most other churches are very welcoming to people who attend concerts, and they're usually very generous with cookies, coffee, and jello mold. They usually won't push their religion on you - but they do like it if you eat hearty. Don't expect gourmet coffee - I don't know why, but churches are tied to those godawful percolators. This is an important thing to know about churches - they really want you to eat, far more than they want you to believe what they believe.

-Joe-