- We've already listed the MAA above, so we'll just mention it here.
- The American Mathematical Society: The AMS is the professional society for research mathematicians in the U.S. This server also has the Combined Membership List for AMS/MAA/SIAM/AMATYC and the MathSciNet search engine for finding reviews of math books and articles.
- Society for Industrial and Applied Mathematics: SIAM is the professional society for mathematicians working outside academia.
- The Association for Women in Mathematics is an association devoted to supporting and promoting women in mathematics.
- American Mathematical Association of Two-Year Colleges: AMATYC is the professional society for mathematicians teaching at two-year colleges.
- National Council of Teachers of Mathematics: NCTM is the professional society for mathematics teachers, and has developed the well-known NCTM Standards for the teaching of mathematics in the schools.