So far, I've talked a lot about the Boy Scouts and the Girl Scouts on this Blog. There is another group that is rapidly growing, the American Heritage Girls.
AHG was started in 2005, by a group of parents that were seeking an all girl program for their daughters, that was more in line with their personal beliefs. As of 2012, they have about 19,000 members in 45 states. (Reference)
AHG is a specifically Christian organization. While there are a large number of overlaps with other scouting organizations, it does not have the interfaith approach that some other organizations do. From what I understand, Religious education is specifically built into the program. It is not specific to one denomination, but it is specifically Christian.
Several protestant denominations and some Catholic churches utilize the AHG program as part of their Children's ministries.
The BSA has also signed a "Memorandom of Mutual Support" with the AHG. I'm not 100% sure exactly what that entails, but some of the things I have seen occur are an AHG presence at Philmont, AHG Leaders are welcome to participate at BSA training events, including Woodbadge, and AHG units are encouraged to sponsor Venture Crews.