Ryan Bates:
Active Record models are the foundation of every good Rails application. Learn how to get the most out of the Active Record features that you use on a day-to-day basis from a popular Rails developer and screencaster. In these screencasts, Ryan Bates incrementally builds the models for a Rails application and refactors them over time to address new features.
Screencasts from The Pragmatic Programmers. $5 per episode.