The National Association of Independent Schools (NAIS) has a podcast The Trustee Table that is perfect for nonprofit board growth and development. It can be used for onboarding of new trustees/directors and ongoing board professional development work. Podcasts usually run 15 to 25 minutes in length.
Here is an excellent, timely podcast sample: "COVID-19 Generative Governance - Board Guidelines from Dr. Richard Chait," Dr. Chait, by the way, is my favorite guru on nonprofit governance. I look at his book Governance as Leadership as the governance bible. New York City heads of school collaborated to have him as a keynote speaker when I was the head at Brooklyn Heights Montessori School in Brooklyn, NY.