CK-12 Online Curricula

This non-profit educational organization provides free online materials (primarily science and math) for teachers and students. They have numerous lessons on biology, including evolutionary theory. Material can be accessed on a topic-by-topic basis or you will find full course-length content including videos, activities, study guides, and even assessments. Their site also allows users to upload their own fully developed lessons designed around the content for sharing with the rest of the online ck-12 community.