This is just an example of some of the free data sets that can be found online.
- Airport, airline and route data 6977 airports, 5888 airlines and 59036 routes spanning the globe
- Awesome Public Datasets on github, curated by caesar0301.
- AWS (Amazon Web Services) Public Data Sets, provides a centralized repository of public data sets that can be seamlessly integrated into AWS cloud-based applications.
- Bioassay data, described in Virtual screening of bioassay data, by Amanda Schierz, J. of Cheminformatics, with 21 Bioassay datasets (Active / Inactive compounds) available for download.
- Canada Open Data, pilot project with many government and geospatial datasets.
- Causality Workbench data repository.
- Chicago Data Portal, an open portal for government data for the city of Chicago.
- Datacatalogs.org, open government data from US, EU, Canada, CKAN, and more.
- Data.gov.uk, publicly available data from UK (also London datastore.)
- Data.gov, public access to datasets generated by the Executive Branch of the Federal Government.
- Data.gov/Education, central guide for education data resources including high-value data sets, data visualization tools, resources for the classroom, applications created from open data and more.
- DataMarket, visualize the world's economy, societies, nature, and industries, with 100 million time series from UN, World Bank, Eurostat and other important data providers.
- Datamob, public data put to good use.
- DataSF.org, a clearinghouse of datasets available from the City & County of San Francisco, CA.
- DataFerrett, a data mining tool that accesses and manipulates TheDataWeb, a collection of many online US Government datasets.
- Delve, Data for Evaluating Learning in Valid Experiments
- Dryad is an open-access repository of research data, focused on scientific and medical research.
- EconData, thousands of economic time series, produced by a number of US Government agencies.
- Enron Email Dataset, data from about 150 users, mostly senior management of Enron.
- Europeana Data, contains open metadata on 20 million texts, images, videos and sounds gathered by Europeana - the trusted and comprehensive resource for European cultural heritage content.
- FEDSTATS, a comprehensive source of US statistics and more
- FIMI repository for frequent itemset mining, implementations and datasets.
- Financial Data Finder at OSU, a large catalog of financial data sets.
- GDELT: The Global Data on Events, Location and Tone, described by Guardian as "a big data history of life, the universe and everything."
- Gene Expression Omnibus, a public genomic data repository.
- GEO (GEO Gene Expression Omnibus), a gene expression/molecular abundance repository supporting MIAME compliant data submissions, and a curated, online resource for gene expression data browsing, query and retrieval.
- GeoDa Center, geographical and spatial data.
- GeoNames geographical database
covers all countries and contains over eight million place names, which can be used to find geocode for countries, cities, suburbs, places and postcodes.
- Google dataset search
- ICWSM-2009 dataset contains 44 million blog posts made between August 1st and October 1st, 2008.
- KidsCount Data Center contains data from state and national sources.
- KDD Cup center, with all data, tasks, and results.
- Kevin Chai list of datasets, for text, SNA, and other fields.
- KONECT, the Koblenz Network Collection, with large network datasets of all types in order to perform research in the area of network mining.
- Linking Open Data project, at making data freely available to everyone.
- Million Song Dataset
- MIT Cancer Genomics gene expression datasets and publications, from MIT Whitehead Center for Genome Research.
- ML Data, the data repository of the EU Pascal2 networks.
- NASDAQ Data Store, provides access to market data.
- National Government Statistical Web Sites, data, reports, statistical yearbooks, press releases, and more from about 70 websites, including countries from Africa, Europe, Asia, and Latin America.
- National Space Science Data Center (NSSDC), NASA data sets from planetary exploration, space and solar physics, life sciences, astrophysics, and more.
- NetworkRepository: Interactive Data Repository, has many collections of graph and networks from social science, machine learning, scientific computing, and other areas.
- Open Data Census, assesses the state of open data around the world.
- OpenData from Socrata, access to over 10,000 datasets including business, education, government, and fun.
- Open Source Sports, many sports databases, including Baseball, Football, Basketball, and Hockey.
- PubGene(TM) Gene Database and Tools, genomic-related publications database
- Quandl, a collaboratively curated portal to millions of financial and economic time-series datasets.
- qunb, a platform to find and visualize quantitative data.
- Re3data, a registry of research data repositories
- Stock Market Confidence Indices, formerly Robert Schiller's data on housing, stock market, and more from his book Irrational Exuberance.
- StatLib, CMU Datasets Archive.
- Time Series Data Library
- UCI KDD Database Repository for large datasets used in machine learning and knowledge discovery research.
- UCI Machine Learning Repository. a collection of databases, domain theories, and data generators
- UCR Time Series Data Archive, offering datasets, papers, links, and code.
- United States Census Bureau.
- Wolfram Alpha disease and patient-level data.