Alfred P. Sloan Foundation: Funds in several categories: Basic Research in science, technology, engineering and mathematics; Science Education; Public Understanding of Science; Economic Performance and Quality of Life.
American Mathematical Society: Offers several funding options, including travel, fellowships to expand skills, and pre-college and college programs that nurture mathematical talent. Awards range from under $5,000 (travel) to over $80,000 (fellowships).
Association for Women in Mathematics (AWM) - Travel Grants: Supports travel for conferences, research, junior faculty to visit with mentors, and collaboration. Awards range from $1,500 to $5,000.
Mathematical Association of America: Offers several grant programs for pre-college programs, undergraduates, and faculty. Average award is $6,000.
National Council of Teachers of Mathematics: Offers research resources and travel grants.
National Science Foundation - Mathematical Sciences: Supports a wide range of projects aimed at developing and exploring the properties and applications of mathematical structures.