GeoAcademy is an open-source GIS curriculum developed by Boundless, a company focused on open GIS solutions. Their courses are designed to be used by instructors in a classroom setting, but they are also available for individual self-study. You can access their materials for free at https://www.geospatial.institute/geoacademy/.

Before enrolling in a course, make sure to check the course syllabus, prerequisites, and reviews to ensure it meets your needs. Additionally, consider the time commitment, format (self-paced or scheduled), and any associated costs.