Apple has recently revised the entire Final Cut Studio section of their website, adding a large amount of descriptions, images, and video training on Motion. You can see some short videos on key Motion features here.

Longer video tutorials on specific features at the following links:

Interface Overview
Working in 3D
Particles, Behaviors, Filters & Keyframes
Creating Titles & Templates
Tracking & Retiming

These tutorials and the other information on the site provide a good overview of Motion’s capabilities.

For more in-depth training on Motion, check out my DVDs available from Ripple Training.