A great resource for strength training for swimmers
One of the many important lessons that Terry continues to reinforce in me is that swimming is an integrated all body movement, not a pull/kick movement. When one accepts this, you realize that the stroke initiates from the HIP, not the arm, and the key to streamlining and swimming longer on your side comes from greater hip rotation. Consequently, much emphasis on more efficient swimming comes from strengthening the core muscles at least as much as any other part of the body.
The book "Complete Conditioning For Swimming" by Dave Salo and Scott Riewald, head swim coach of USC & former head of bio-mechanics for USA Swimming respectively, is an exceptional reference and even has a DVD demonstrating many of the exercises. While working extensively on core exercises, it has many great dry land swimming oriented workouts from beginner to advanced.