Open Curriculum provides more than just a collection of mathematics lesson materials. In your Open Curriculum account you can create and share your own lessons and units of study. You can also upload existing materials to incorporate into the lessons and units that you create in Open Curriculum.
Applications for Education
Open Curriculum advertises that English and science lesson materials are coming soon. In the meantime the math resources and lesson planner will give you a good sense of how the service functions. The sharing aspect of Open Curriculum could be useful for large departments that are looking for a place to share materials that they like and create with each other.
H/T to Larry Ferlazzo.