Does your ancestor's marriage license or record list the name of the minister, but nothing else? Try searching for him either at http://www.google.com/ or http://books.google.com/. I tried it on a minister in Chicago who used his name and address (but no church name) on a marriage record--Google found him on the history page of that church.
I used google books on the name of a minister from a Culpeper County, Virginia, marriage in 1806 and found out quite a bit about him.
If the name gives results that are too broad, try adding the name of the city/town or county where the marriage took place.