Site to look for Congressional Research Reports on a wide variety of topics.
Looking for think tank reports
I recommend looking for these last. Read your newspaper articles, scholarly articles, and government reports to see if any think tanks are mentioned. If yes, visit their websites.
If you still haven't found a reputable think tank, try here:
This customized Google search will search the websites of institutions that generate public policy research, analysis, and activity. These sites are affiliated with universities, governments, advocacy groups, foundations, and non-governmental organizations.