Sal Khan of the Khan Academy offers four different models for blended learning in this 11-minute video.
I wanted to call out his graph that shows the interplay between breadth and depth (see below). Sal argues that an instructional model that uses digital technology to ensure students master core skills would allow schools and teachers to focus more of their time focused on expanding breadth and/or depth. This is not a futuristic vision either; blended schools are already blending the best of technology and teacher-facilitated instruction in new and interesting ways. For instance, Summit Public Schools in the Bay Area has adopted Khan Academy as part of a holistic approach to math instruction that also includes teacher-facilitated project-based learning and other applications of core knowledge and skills. As digital content improves and scales to more schools and classrooms, and as teachers and schools become more comfortable building lessons upon those tools, we expect many, many more promising examples like this to emerge.