I believe that any educator should know the basics of their profession. Pedagogy, child psychology, learning theories - all provide a sound ground from which to build.

Learning Theories - Behaviorism, Constructivism, Cognitivism, Design-based etc.

More Learning Theories

Daniel Willingham - Cognitive psychologist. Excellent articles on learning, cognition, memory, motivation etc.

Teach It So - Dr. Mark Evans debunks edu myths (learning styles, homework etc) using research-based evidence.

Teachers Toolbox - Another website from Cambridge Regional College that focuses on learning theories and research.

Juxtaposition - Articles ranging from knowledge and learning principles to pedagogical frames and memory.

Educational Psychology (PDF) - A must-read for any educator. Yes, 364 pages but critical to understanding development, cognition, learning.

Learning and Forgetting Lab - Robert Bjork, cognitive scientist (text and videos)

Neuroscience and the Classroom- Insights from neuroscience that can support teaching in the classroom (videos, visuals, teaching course etc).

Thinkers in education - Freire, Pestalozzi, Giroux...all here.

Educational Theory - all issues