U.S. Department of Education: Scholarship Scams
https://studentaid.ed.gov/sa/types/scams
Peterson’s Myths About College Scholarships
https://www.petersons.com/college-search/myths-about-college-scholarships.aspx
National Science Foundation Specialized Information for Graduate Students
http://www.nsf.gov/funding/education.jsp?fund_type=2
Many professional associations provide information about subject-specific fellowships and grants on their websites. Look for associations related to your discipline.