Cross-disciplinary data repositories, data collections and data search engines:
Single datasets and data repositories
http://archive.ics.uci.edu/ml/
http://crawdad.org/
http://data.austintexas.gov
http://data.cityofchicago.org
http://data.govloop.com
http://data.gov.uk/
http://data.medicare.gov
http://data.seattle.gov
http://data.sfgov.org
http://data.sunlightlabs.com
https://datamarket.azure.com/
http://developer.yahoo.com/geo/g...
http://econ.worldbank.org/datasets
http://en.wikipedia.org/wiki/Wik...
http://factfinder.census.gov/ser...
http://ftp.ncbi.nih.gov/
http://gettingpastgo.socrata.com
http://googleresearch.blogspot.c...
http://books.google.com/ngrams/
http://medihal.archives-ouvertes.fr
http://public.resource.org/
http://rechercheisidore.fr
http://snap.stanford.edu/data/in...
http://timetric.com/public-data/
https://wist.echo.nasa.gov/~wist...
http://www2.jpl.nasa.gov/srtm
http://www.archives.gov/research...
http://www.bls.gov/
http://www.crunchbase.com/
http://www.dartmouthatlas.org/
http://www.data.gov/
http://www.datakc.org
http://dbpedia.org
http://www.delicious.com/jbaldwi...
http://www.factual.com/
http://research.stlouisfed.org/f...
http://www.freebase.com/
http://www.google.com/publicdata...
http://www.guardian.co.uk/news/d...
http://www.infochimps.com
http://www.kaggle.com/
http://build.kiva.org/
http://www.nationalarchives.gov....
http://www.nyc.gov/html/datamine...
http://www.ordnancesurvey.co.uk/...
http://www.philwhln.com/how-to-g...
http://www.imdb.com/interfaces
http://imat-relpred.yandex.ru/en...
http://www.dados.gov.pt/pt/catal...
http://knoema.com
http://daten.berlin.de/
http://www.qunb.com
http://databib.org/
http://datacite.org/
http://data.reegle.info/
http://data.wien.gv.at/
http://data.gov.bc.ca
https://pslcdatashop.web.cmu.edu/ (interaction data in learning environments)