I guess I'm not sure what kind of data you're looking for.
I don't think the data set exists that says "Nonprofits are/are not tax-shelter scams that spend most of their time doing shady bookkeeping".
I don't know if there's a data set that breaks down how many people get helped by nonprofits, either, because the stuff they do takes on so many different forms (and how would you quantify the work, say, an environmental nonprofit does in terms of human benefit?).
I do know that, if you were curious, there is a very far-reaching community of nonprofit professionals online, and they'd do a much better job than me explaining the social-benefit-type of work their employers do.
I'll ask around tomorrow, too (I have a bunch of nonprofit-employed friends, who work in programs and not administration). I'll return to this thread if I get anything good to share.
(And yes, there's definitely corruption in the nonprofit world, I won't argue with that, my beef is with churches that do almost nothing for the community and still enjoy the tax-exempt status and that "we're a charity, ergo we're good for the world" sentiment.)