Ok, some basic websites to start looking (keyword - pianist or accompanist):
Presbyterian Association of Musicians
National Association of Pastoral Musicians (Catholic)
These are less specific as far as denominations go:
That just gets you started - Google is an amazing thing, usually if you combine a few key word like city/state | pianist | accompanist | church you'll come up with quite a few hits. I have an RSS feed of Craigslist and Google that saves a lot of time.
As for the music that you play, that depends upon numerous things. The music director, first of all, but also the age and musical tastes of the congregation. Services can be traditional, contemporary, or something they call 'blended worship'. Translated, that is Hymnal, organ and piano vs Contemporary Christian, electric keyboard and band vs a mix of both.
A classical pianist confronted with contemporary christian sheet music may experience a range of emotions. Amusement, confusion, pain - these are all normal. Because their music comes in many, many forms, often without the small, black, reassuring notes and rhythms we like so much. Charts are very common, and sometimes, just the lyrics are given to you and you scribble in the chords. Sometimes the charts have wrong chords, are in the wrong key, or have wrong chords in the wrong key. If you are working with untrained musicians, they won't realize this until you are in the middle of the song and it sounds off. If you find yourself in this situation, breathe deep, get a pencil, and start rewriting the *cough* music to suit your needs.
You will probably play "Open the Eyes of My Heart" several times, so go ahead and learn it.
Other odds and ends - at the Catholic gig I was at, I played Ave Maria in every key possible. Also know Here I Am, Lord and On Eagles Wings. While I was there, I did over 50 weddings. Most of them had Canon in D, Jesu Joy of Man's Desiring, the Wedding March and the traditional Wedding Fanfare closer. Also: 'the Prayer' and 'How Beautiful'(Twyla Tharp). So learn those tunes, and you're halfway home.
Finally, get some arrangement books of church music. You'll need them for preludes, postludes, offertory and communion music. ark Hayes is a good place to start, most of his arrangements are great. I also like Fred Bock, Don Wyrtzen, Bill Wolaver, Carl Seal, etc. Chuck Marohnic wrote some great jazz arrangements, if you are looking for something different. I have a stack of arrangements, some books better than others. If you have any suggestions, please add on.