Sources

Another site to background nonprofits and analysis data is GuideStar.  GuideStar is specifically geared towards nonprofits; this is a great watchdog site, one can background a charity before they contribute to it.  There are also interesting lists on GuideStar, like the most searched nonprofits in the last month. GuideStar also encourages nonprofits to update their forms and reports in order to get the 'GuideStar Exchange Seal' on their reports, which helps their credibility.  When looking at 990s and form 1023 it is important to be very speculative..the more questions asked the more credible the nonprofit may be, or possibly more corrupt.
http://www2.guidestar.org/

The U.S. census bureau is also a trusted site when it comes to business statistics and information. There is a specific tab for businesses and nonprofits with multitudes of tables and information.   There is also a breakdown of how much each state contributes each year.  This site is especially useful for comparing data sets of information.

http://factfinder.census.gov/home/saff/main.html?_lang=en