Massive Open Online Courses (MOOCs) provide tremendous opportunities to study the learning behavior of diverse student populations at unprecedented scale. In the past year, MITx and HarvardX have successfully delivered over a dozen MOOCs through the edX platform; leading nearly one million registrants generating well over a terabyte of click-stream data. So who are these registrants? And how does leaner behavior vary from course to course? This talk will address these issues by exploring self-reported demographics and highlighting exploratory work on metrics involving resource use, with particular emphasis on lecture video interactions.