The following pages contain compilations of links to public data sources for various subjects. Many of the sources are free:
The Kauffman Foundation is one of the largest private foundations in the United States. Established in the mid 1960s by the late entrepreneur and philanthropist Ewing Marion Kauffman, the Foundation focuses on education and entrepreneurship, which Ewing Kauffman viewed as two ends of a continuum.
The link above lists data sources that reviewers have used in building the State of the Field, a compilation of knowledge on entrepreneurship research written by experts in the field.
Also, see the "data sources" section in each State of the Field topic area for overviews of the best data sources for various types of research topics. (source: website)