Prayer is a topic covered often by atheists, but it still bears discussing.
There are several kinds of prayer. As far as I can tell, they can be covered in three sections. The first is the phenomenon of asking God for something, the definition treated by many atheists to be synonymous with prayer. the second is almost the opposite, prayer as means of learning what God wants you to do: the third and final is similar, prayer as a way of simply becoming closer with God.