Harvard's Kennedy School provides a Google custom search that will search Web publications from a large number of 'think tanks'. Enter your search term(s) in the box as in any Google search. Most of the materials will be freely available.
There's a lot of great -- and often scholarly -- information available for free online. The Open Access movement has resulted in many rigorously reviewed collections of scholarly information available free online.
Open Access Journals
Other Open Access Resources
You can also find highly credible information other than scholarly content online. There are advanced ways to search Google, and to use Google for your research.