While looking at Martin and Shan Graebe's website I stumbled across a hidden treasure and an act of huge generosity.
Shan is a speech and language therapist, and has put together some really excellent notes on the mechanics of singing here. They cover everything from breathing to range and power and from keeping your voice healthy to how to memorise songs.
I don't know either Martin or Shan personally, but I'd like to thank them for making the resources freely available and recommend them to anyone who sings.