How would you advertise it

Yea - drop your business card in the collection plate... KIDDING! Other than bidding on Google AdWords, I don't think there is a tasteful way to do that.

I'm stumped.

Maybe just do what these people did and carve out a niche and specifically target churches with your domain name and whatnot.

Online and offline same.
Its depend on you, which ways do you want use?
Online, we can use SEO and ads or banner to promote your site.
Offline, you can use brochure for support that.

You can use social bookmarking and social networking to promote your services..

There are many way on how to advertise it.

Write original articles and submit them to article directories. Use your website in your resource box and people will visit your website if the article intrigues them enough.

Submit your website to link directories. The more exposure and back links to your site you can get, the better. Find link directories that are popular and have lots of traffic and you’ll have visitors in no time.

Place online and offline classifieds. Find classified sites, there are paid and free, and submit eye catching ads. Make the title pop so people will instantly be drawn to it.

Hand out flyers with your website address on them. Make flyers with a slogan or picture that will make people stop and look at it. Don’t be afraid to use some color.

Make a nice interesting video about your service and post it in video sharing sites, then promote each video posting in every social bookmarking possible this should bring you relevant visitors.

Ben