Federal Reserve Bank of St. Louis · Market & fundamentals data
In-depth entry
Free economic database from the St. Louis Fed aggregating hundreds of thousands of US and international time series, with graphs, vintages (ALFRED), an Excel add-in and a keyed JSON/XML API
Bloomberg L.P. (FIGI Registration Authority) · Market & fundamentals data
Free API and web tool from Bloomberg for mapping tickers, ISINs, CUSIPs and other identifiers to public-domain FIGI instrument identifiers, with search and filter endpoints
Statistics Canada (Government of Canada) · Open & public data
In-depth entry
Canada's national statistical agency publishing census, economic and social data tables with open licensing and programmatic access via Web Data Service