NASA - NASA offers access to both its Education and Public Outreach resources as well as a support network for everything related. See also the Explanatory Guide to the NASA Office of Space Science Education and Public Outreach Evaluation Criteria (March 2004).
NSF - Links to programs and grants for K-12, undergraduate and graduate education, informal education and education research.
Department of Education - Links to education resources for preK-12, higher education and adult education, as well as to policy, grants, and research.
NASA's Science Mission Directorate (formerly the Office of Space Science) - Sample EPO Proposals and Plans
Performance Metrics for NASA's SMD EPO Programs - A resource guide for anyone concerned about the potential elimination of the education and public outreach (EPO) activities in NASA's Science Mission Directorate (SMD), as called for in President Obama’s fiscal year 2014 budget proposal.
The Ancient Universe: How Astronomers Know the Vast Scale of Cosmic Time. A guide for Teachers, Students and the Public. Published by the AAS in 2004.
The Process of Science: and its Interaction with Non-Scientific Ideas. A guide for Teachers, Students and the Public. Published by the AAS in 2007.