Bernard Marr wrote a post Big Data: 33 Brilliant And Free Data Sources For 2016. He gives a list of free data sources provided by governments, social websites and companies including Google and Facebook. The data types include census, climate, financial, health, news, etc. I have found the list very interesting. Springboard "19 Free Public Data Sets For Your First Data Science Project" has good information about free data sets such as United States Census Data, FBI Crime Data and CDC Cause of Death etc.