You should really listen to the whole thing, but I want to share two points from his talk that were especially interesting.
First of all, this miracle of Jesus buttresses the authenticity of the the Gospel account. Consider: if you were an author charged with the publicizing of a powerful figure and fabrication of that person's biography, "you would never invent for your inaugural sign a miraculous solution to a mere social embarrassment [the master of the banquet did not plan well enough and ran out of wine]." The only logical conclusion is that this event must have happened.
Second, Keller does what I consider to be a deft and accurate handling of the question: why this miracle? I'm withholding a thorough explanation because I want you to listen to the whole message, but I will share one thought, in which Keller quotes another minister.
"Jesus Christ is sitting in the midst of all this joy, sipping the coming sorrow. Why? Because there is no way that Jesus Christ can think about what it will take to give His bride the cup of joy and gladness without thinking about the cup He was going to drink."The miracle of turning water into wine at that wedding feast was a profound foreshadowing of the excruciating passion that must occur before the joyful consummation of the Son of Man united with His Bride.
Jump here to listen to Lord of the Wine by Timothy Keller

The stone had a very special significance. The previous year, I had taken a solo motorcycle trip to Utah and while I was there I gathered five water-smoothed stones from a stream up in the mountains. Now it just so happens that I have five sons. In my prayers for them, I have often thought of them as the five smooth stones David collected from the stream before facing Goliath. I imagine he intended each one to deliver a death blow to some nasty giant. Kind of in the same way, I pray that God would use each of my boys to scatter bad guys like doubt, compromise, fear, deception and darkness in people's lives. I told my son how that stone represented God's desire to use him to slay giants.
