According to two early Islamic historians, Ibn e Saad and Ibn Hisham, the Prophet Muhammad allowed a delegation of 60 Byzantine Christians from Najran in Yemen to worship in his own mosque in Madina. The story goes like this: the Christians had come to discuss a number of issues with Muhammad. When it came time for them to have a church service, they asked the Prophet's permission to perform their service in the mosque. Muhammad answered, "conduct your service here in the mosque. It is a place consecrated to God."
Now, Aldersgate United Methodist Church in Virginia will allow Muslims to pray there on Fridays while a nearby Mosque is being renovated.
Why does an Atheist care about this? Because it helps strengthen the faith I have in humanity. These are people that understand that they worship the same invisible magical friend. No, I don't believe in their invisible magical friend, but it's nice to see that these two representative groups do actually read their respective scriptures, and understand history.