Many governments publish open data they produce or commission on official websites to be freely used, reused, or redistributed by anyone. These sites are often created as part of open government initiatives.
Some open data sites like CKAN and DKAN are open source data portal solutions where as others like Socrata are proprietary data portal solutions.
The data sites provide interfaces based on Data and Metadata standards like Dublin core.
Some countries have unofficial open data portals created citizen initiatives or published by non-governmental organizations.