Gracias a Bernard Marr , que ha realizado esta muy buena y útil recopilación, para muchos de los que trabajáis con datos abiertos, big data, visualización, periodismo de datos, etc...
Data.gov http://data.gov
US Census Bureau http://www.census.gov/data.html
European Union Open Data Portal http://open-data.europa.eu/en/data/
Data.gov.uk http://data.gov.uk/
The CIA World Factbook https://www.cia.gov/library/publications/the-world-factbook/
Healthdata.gov https://www.healthdata.gov/
NHS Health and Social Care Information Centre http://www.hscic.gov.uk/home
Amazon Web Services public datasets http://aws.amazon.com/datasets
Facebook Graph https://developers.facebook.com/docs/graph-api
Gapminder http://www.gapminder.org/data/
Google Trends http://www.google.com/trends/explore
Google Finance https://www.google.com/finance
Google Books Ngrams http://storage.googleapis.com/books/ngrams/books/datasetsv2.html
National Climatic Data Center http://www.ncdc.noaa.gov/data-access/quick-links#loc-clim
DBPedia http://wiki.dbpedia.org
Topsy http://topsy.com/
Likebutton http://likebutton.com/
New York Times http://developer.nytimes.com/docs
Freebase http://www.freebase.com/
Million Song Data Set http://aws.amazon.com/datasets/6468931156960467
