The UCI maintains 413 datasets, as of 1/10/2018, for machine learning: http://archive.ics.uci.edu/ml/index.php. The following screenshot shows the top three downloaded datasets:
For the number one downloaded dataset called Iris, we have the following information:
The beauty of these datasets is that they give quite detailed information such as the source, the creator or donator, a description, and even citations.
The following table shows several potential public data sources for users in the area of data science and business ...