http://en.wikipedia.org/wiki/Think_tank

A think tank (or policy institute) is an organization that conducts research and engages in advocacy in areas such as social policy, political strategy, economics, military, and technology issues. Most think tanks are non-profit organizations, which some countries such as the United States and Canada provide with tax exempt status. Other think tanks are funded by governments, advocacy groups, or businesses, or derive revenue from consulting or research work related to their projects.[1] The following article lists global think tanks according to continental categories, and then sub-categories by country within those areas. These listings are not comprehensive, given the more than 4,500 think tanks that McGann includes in his database. In general, this article is an introduction to the think tank landscape, and provides a way to quickly click-through to those of interest.