Below is a great article on how to talk to someone who has experienced and is living with suicide With the death of Rick Warren's son this will probably be a hot topic in many circles. This article does a great job give advice on how to talk, interact, and offer support to those who are dealing with the suicide of a loved one.
In one of my files I have a great sermon that a minister preached at the funeral of one of his church members who died of suicide. In it he says, "In that moment _________ lost sight of the promise that was made by God at his baptism, but today we can rest assured that God has never forgotten." That has always stuck with me and if or when I am called upon to do a service like that, I will be quoting that exact phrase.
All pastors should be prepared and ready for when this happens in our congregations. Chances are it will if it hasn't already.