Most Christian sites on Islam have material explaining the Christian faith, including answers to Muslims misconceptions, as well as articles stating why they do not believe that Islam is truth. As a navigational help the below sites are sorted in two categories depending on their main focus.
|What Christians Believe||Critique of Islam from a Christian Perspective|
Material on particular movements: Ahmadiyya, Nation of Islam
Some more thoughtful Christian pages: 
And really very different from all the above:
A visual tour on the identity of Jesus Christ, the Word of God.
Answering Islam Home Page