Wikidata Can access data here. May be used with Mix'n'match which can lists some entries of external databases and allows one to match them against Wikidata items
CKAN, an open source data management system (DMS) for powering data hubs and data portals
DataCite, a leading global provider of DOIs for research data
Datastro.eu, an open data portal about astronomy (e.g., all Apollo program pictures, light pollution maps, NASA and Minor Planet Center data, asteroids, orbits, exoplanet catalog, Messier catalog, sunspots reports, constellations list)
DMPonline, Tool for creating, reviewing, and sharing data management plans
