Is Allah God?
From Desiring God:
Update: For those unfamiliar with "A Common Word," it's a letter written to Christians by 138 Muslim scholars last October saying that love for God and love for neighbor is common ground between Christianity and Islam. The response from the Christian leaders, which John Piper finds disappointing, was published the following month.
Another Update: Justin Taylor suggests, "For those who want a fuller unpacking of Piper's views of these issues, I would recommend his essay, Tolerance, Truth-Telling, Violence, and Law: Principles for How Christians Should Relate to Those of Other Faiths, written in 2002."