Free data sources

EODData – free EOD data for US equities and a few others

Google Finance – free EOD data for US equities

Yahoo Finance – free EOD data for US equities

Dukascopy – Free Historical Data Feed mainly FX

Finam – Russian site that offers free up to 1min intervals for different investment vehicles

Stooq – Free bulk download of many different equities around the world EOD or 1h or 5min

Wealth Lab Wiki – No idea, just came across and wanted to document in case I need it in the future

Data quality is important and I would not use any of these sources to build an extremely sophisticated strategy that e.g. aims to explore potential short term arbitrary opportunities… I am simply using them for my more general analysis and deal the results with care.