GuideStar
Provides detailed information on over 850,000 nonprofit organizations. Includes ‘IRS-registered 501 nonprofit organizations that may accept tax-deductible contributions’. Profiles cover mission and programs, financials, leaders, and most importantly, full text via PDF of the charity’s IRS 990 filing from 1998 forward in most cases. Form 990 provides information on revenues, expenses, programs, activities, executive salaries and board members.