Open data is free, publicly available data that anyone can access and use, without restrictions. Businesses, nonprofits, governments, and citizens use open data to launch new initiatives and ventures, analyze trends, make data-driven decisions, and solve complex problems in all sectors of the economy.
US Federal Government Open Data Resources.
"Here you will find data, tools, and resources to conduct research, develop web and mobile applications, design data visualizations, and more." Data.gov is a centralized resource for open data sets created by entities of the United States government.
US Open Data
The U.S. Open Data Toolkit is designed to help federal data providers and data to locate US data from many agencies and in many formats. Provided by the Center for Open Data Enterprise (CODE), a 501(c)3 nonprofit organization whose mission is to maximize the value of open government data.
A project of the National Oceanic and Atmospheric Administration, Climate.gov is an example of a government resource developed to provide access to a wide variety of data on a specific topic, the climate of planet Earth.
European Open Data Portal
Collection of data sets from European Union countries
Directory to searchable databases containing open data from many countries and regions.
Collection of all kinds of data -- data sets, statistical tables, general profiles of countries.
Global registry of research data repositories that covers research data repositories from different academic disciplines. It includes repositories that enable permanent storage of and access to data sets
Search engine with links for data published by central government, local authorities and public bodies in the UK concerning education, health, environment, maps, crime, etc.
Google Dataset Search
Searches for datasets hosted in thousands of repositories across the Web