Think tanks are non-profit organizations created to research and promote public policy, often with a focus on a particular issue or espousing a particular political persuasion. Think tanks employ lots of Ph.D.s who conduct resarch and write papers with the aim of influencing legislation. They can be excellent sources of information as long as you keep in mind their purpose or agenda.
Here's a list of conservative think tanks
and Policy Institutes
From the Carnegie Endowment for International Peace
From the Univ. of Michigan.
A large list from NewsMax.com
Provides links to sites about popular issues such as immigration, tax reform, secondhand smoke, affirmative action, social security reform, and more.