Randi Eckstein grilled Elecia White (@logicalelegance) on inertial sensors: when to use accelerometers vs. gyroscopes; gyroscopes vs. rate sensors; how to make an inertial measurement unit; the basics of quaternions and Kalman filters; what products need which sensors (and why).

Other good resources:

Sensor Wiki (excellent visualizations)
Guide to using IMU (step by step practical information starting with ADC capture)
Sparkfun inertial sensor buying guide (descriptions on what's available and how to differentiate between them)