Good tutorial sites touching various subjects and features related to FSX.
Angle of Attack
Chris Palmer created a comprehensive 90-day flight simming training course to simmers for free. It is particularly useful to beginners and all who want to polish up their aviating skills.
Eric Krueger has posted a series of six tutorial videos about the setup of EZdok, a camera and effects system developed by EZdok Software for FSX. It basically covers all key points from the very basics to some advanced features in EZdok.
Free Checklists NEW
Freechecklist.net offers a number of highly accurate aircraft checklists for Flight Simulator.
A site built by Noel Kruse who offers a series of “Fly Better” books about how to fly aeroplanes. Although it is for real flying, the information is useful for all flight-simmers who want to improve their knowledge and skill.
List will be updated once available.