Camera Instructor is a free web-based photography school that teaches you the fundamentals of photography through videos and interactive exercises. It's taught by photographer and programmer Cody Meyer, and each lesson starts with an instructional video followed by mini exercises (using in-browser camera simulators) that test what you learnt.
There's only one course available now, Photography 101 — with eight lessons covering the exposure triangle and shutter speed, but courses on portraits, landscapes and weddings are in the works. Even with only eight lessons so far, the site is a nice resource for those who want to get more out of their camera and are new to photography fundamentals.
Camera Instructor makes money through affiliate links for things like camera accessories (surprise!).