Ars Mathematica - News and discussions on the mathematical arts.

The Institute of Mathematics and its Applications Discussion Forums - Discussion of mathematical issues with councillors and members of the UK professional body, open to all.

Javamath-discuss - A general mailing list for discussion about mathematical software development in Java.

JISCmail - Mailing lists in mathematics and statistics for the UK academic community.

Math Forum: Public Discussions - Group topics include general math, education, geometry, software, calculus reform, research and recreations.

Math Help Forum - A discussion forum for students and teachers of mathematics at school, college and advanced levels, including homework help for students.

Math is Fun Forum - A discussion forum for K-12 math students and teachers, with a focus on learning and teaching math the fun way.

Mathiverse Forums - A mathematics and physics forum with many categories ranging from pre-algebra to topology and particle physics.

Maths-Education - Email forum for those working in mathematics education to share ideas and experiences, and request information.

Mathstore Electronic Discussions - A list of mailing lists compiled by LTSN.

My Math Forum - Active forum for a better understanding of mathematics. Includes puzzles and riddles and some solved problems.

Undernet Math - Topica email list serving the users of the IRC channel #math on the Undernet, for discussion and challenging puzzles.

Yahoo Groups : Erdos - A group for proposing problems, sharing ideas, discussing areas of research and reviewing papers and books of interest. [Requires Yahoo! membership]

Yahoo Groups : Maththeorists - Discussions relating to number and mathematics philosophy.

Yahoo Groups in Mathematics - Mailing lists and discussion groups (including former OneList and eGroups).

Yahoo Groups: Math For Fun - Focuses on solving challenging math problems.

Yahoo Groups: Theory-edge - Informal discussion of research in algorithmics, mathematics, and their applications.