Giving USA  reports that in 2009 -  for the third year running - private contributions to nonprofits exceeded $300  billion.   As usual, most giving comes from individuals - not grants.   Even federal grants to nonprofits, at $38 billion in 2008, are dwarfed by the $227 billion given by individuals.   You can get analysis of the Giving USA report in the Chronicle of Philanthropy.

Some  nonprofits use Giving USA to see how their fundraising efforts size up.   Another good source for this "benchmarking" is the National Center for Charitable Statistics, which publishes the Nonprofit Almanac.    For more ideas  get the book  Benchmarking for Nonprofits.  

Don't hesitate to ask a librarian if you're digging for data: that's what we're here for!