iTrain - Natalie Coughlin Backstroke Tips
Comments: Body position. Rotation. Shorten your exit.

GoSwim - Backstroke - Single Arm Drill
Comments: How to do the single arm drill (or all drills for that matter: deliberately).

GoSwim - Backstroke - 4 Back 3 Free Drill
Comments: This is a great drill to improve both strokes and to drive home the point that the backstroke pull is basically a freestyle pull done on your back!

YouTube - Ryan Lochte - Backstroke Technique
Comments: Excellent footage from several angles.

YouTube - Backstroke - Hagiwara Tocomo
Comments: This is Japanese, but just watch her technique.

GoSwim - Backstroke - Steady Kick
Comments: Good details on the backstroke kick.