American Alliance of Museums
AAM provides Tier 3 museum members with sample interpretive plans, and interpretive clothing policies.
National Association for Interpretation
The National Association for Interpretation shares Standards and Practices for Interpretive Planning (PDF).
National Park Service
The National Park Service (NPS) presents Planning for Interpretation and Visitor Experience, which discusses the elements of an interpretive plan: the desired visitor experience, essential stories, the mix of media and personal services, and the staffing, collections, and research needs to implement the plan. It includes a bibliography (PDF).