Actually, it's part of the 990s that they have to file, and those 990s are part of public access. Guidestar.org provides the PDF files. You can pull up a particular "charity" like Planned Parenthood in a certain region, and see where their money comes from. They are supposed to provide a list of donors, but those donors are often foundation "fronts." Or you can see where a particularly charitable foundation disperses its own funds.
What I'd like is a cross-referenced spreadsheet.
Whatever, but I've never seen a donor list provided for a 501c3 in their 990 filings.... By the way not all non profits are listed on Guidestar..