Foundation Center – Requires registration for all the services but there is a fair amount to be found for free. Look under Fund Finders …990 Finders for a charities form 990.
Giving Institute – formerly American Association of Fund-Raising Council Trust for Philanthropy – AAFRC
National Center for Charitable Statistics Urban Institute – Must sign in as a quest to get stats on charities/nonprofits.
Statista – Up-to-date statistics (charts & graphs), studies, reports and forecasts from over 18,000 sources. Coverage is international and can be downloaded in PNG, PDF and XLS format files.