This guide is intended to provide a starting point for those developing proposals and projects designed to broaden participation in science, technology, engineering and mathematics (STEM) through informal learning experiences. It is an outcome of an Association of Science-Technology Centers (ASTC)/Center for Advancement of Informal Science Education (CAISE) digital resource curation workshop (August 5, 2016) where participants identified relevant projects from the InformalScience.org database. This digital resource complements the synthesis report of the Leadership Workshop for Achieving Scale