A couple of months ago I placed a link in the sidebar for The Gospel Coalition. If you haven't taken a chance to visit the site, I'd like to encourage you to listen to the media that is available. Be sure to start with Don Carson's address, What is the Gospel? where he digs into 1 Corinthians 15. The gospel is so rich, deep, and wonderful. I hope that we never grow tired of being reminded of that which is "of first importance." So, listen and be reminded of the greatness and graciousness of God.
If you want to listen or download an mp3 of Carson's address, go to the link above. If you'd rather read a transcript, you'll find that here.