The Gospel Coalition website (which has gone from a little helpful toward really helpful in a short period of time) has a number of short video interviews (linkable) with key players: Don Carson, John Piper, Mark Driscoll, and yes, Tim Keller. As you could have guessed, I'm linking the Keller (and Carson/Keller) ones here for you. To see them more quickly, just go to the interviews page and scroll to them. And don't forget to visit my Tim Keller Resources page.
Tim Keller - What do you see yourself doing in The Gospel Coalition? | m4v
Tim Keller - What is the state of the pulpit in America today?| m4v
Tim Keller - How does preaching affect how christians see culture?| m4v
Tim Keller - What do you tell pastors about their family life? | m4v
Tim Keller - What ways can people learn from your teachings | m4v
Don Carson & Tim Keller - What started The Gospel Coalition? | m4v
Don Carson & Tim Keller - What makes The Gospel Coalition different? | m4v
Don Carson & Tim Keller - Assessing The Gospel Coalition | m4v
Don Carson & Tim Keller - How were the leaders of The Gospel Coalition gathered?| m4v
Don Carson & Tim Keller - What is the future of The Gospel Coalition? | m4v
Don Carson & Tim Keller - What threats and challenges face The Gospel Coalition? | m4v
Don Carson & Tim Keller - What causes fragmentation in evangelicalism today? | m4v