Lhivera’s Compendium
Sorry it's been so quiet here for so long; my limited game time has mostly been dedicated to testing, improving SimulationCraft, and working on this thing I'm about to show you.
Lhivera's Compendium is the evolution of my old stickied "Non-Obvious Mage Mechanics" thread from the Mage forum. It's not intended to teach you how to play a Mage well — I'm a terrible teacher, other people do that sort of thing much better than I do — but rather to explain how various Mage mechanics and abilities work. It isn't complete, and will probably always be a work in progress, but there's enough there for people to start taking a look at, and there's a form where you can pose questions that aren't answered if there's some Mage mechanic that you don't understand.