Check out:
http://www.guidestar.org/
It isn't the easiest to get through to find your agency, but there are ways to navigate without paying the fees for the extra reporting.
We checked out our agency and their tax filing is right there for you to see how much the top people are earning. It can be pretty sad to see a non-profit where the top person makes 350,000 per year before her additional profits (health insurance, etc).
Good luck!
C