A list of previous and future OGC sprints and hackathons is available at https://www.ogc.org/projects/initiatives/ogcsprints
OGC API website, https://ogcapi.ogc.org
Blog posts about previous sprints, https://ogcapi.ogc.org/#blogs
OS Open Zoomstack, https://os.uk/business-government/products/open-zoomstack
ESA Copernicus Open Access Hub, https://scihub.copernicus.eu/dhus/#/home
NASA Open Data, https://open.nasa.gov/open-data/
JAXA Data Distribution service, https://www.eorc.jaxa.jp/en/distribution/