FRED

(Aggregate Time series data of US and other countries)

Ipums

(Armonazied Cross-sectional data from the US and other countries)

Social Explorer

(Geographic Census Data)

Data.gov

(Repository for Government Data)

INTAN

(Intangible Capital Data)

World Bank

(Aggregate Socio-Economic Data)

ProPublica

(Collection of free and pay datasets used in journalistic research)

538

(Political and Sport Data)

Kaggle

(Various Datasets)

IMF

(Aggregate International Financial Data)

Investigative Reporters

(Collection of free and pay datasets used in journalistic research)

SEDAC

(Spatial Satellite Data)