This wide-ranging and informative online course from Annenberg Learner can be a powerful resource for both high school and K-8 teachers. The site features 10 two-and-a-half hour sessions on a range of related topics, starting with an overview of Algebraic Thinking, moving through Patterns in Context, Functions and Algorithms, Proportional Reasoning, and other topics before finally culminating in a section that utilizes Classroom Case studies. Along the way, a series of edifying and entertaining videos and interactive web activities keep the material fresh, while the various support materials help explain everything from simple equations to some of the more complex topics in the course. Though it is possible to register for the course and take it for credit, interested teachers can also simply learn at their own pace and on their own time.