Motorcycle Physics

I've been fascinated by motorcycles since I was a child. I've owned and ridden them since I was a teenager. What keeps a motorcycle on two wheels? What are the physical forces behind the simple (OK, not so simple) act of riding a motorcycle?

Lean angles, countersteering, force vectors, rotational velocity, inertia, inverted pendulums... what's with all this stuff?

This site is a great place to learn about motorcycle physics and related topics. As I find useful books and articles about motorcycle physics, I'll post them on this site.