Math Forum: Public Discussions  
   Group topics include general math, education, geometry, software, calculus reform, research and recreations.
   http://mathforum.org/discussions/

Yahoo Groups: Math For Fun  
   Focuses on solving challenging math problems.
   http://groups.yahoo.com/group/mathforfun/

Talk Math  
   A dicussion forum for students and teachers. Topics discussed include Algebra, College Algebra, Calculus, Trigonometry, Geometry.
   http://www.talkmath.com/

Yahoo Groups in Mathematics  
   Mailing lists and discussion groups (including former OneList and eGroups).
   http://dir.groups.yahoo.com/dir/Science/Mathematics

Topica: Science/Mathematics  
   Mathematics-related e-mail lists.
   http://www.topica.com/dir/?cid=195

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

Yahoo Groups : maththeorists  
   Discussions relating to number and mathematics philosophy.
   http://groups.yahoo.com/group/maththeorists/

Maths is Toothpaste  
   Mathematics is useless on its own, it only has a function when used with something else (i.e. a toothbrush). An online discussion.
   http://www.mathsistoothpaste.org/

Yahoo Groups: Theory-edge  
   Informal discussion of research in algorithmics, mathematics, and their applications.
   http://groups.yahoo.com/group/theory-edge/

Mathstore Electronic Discussions  
   A list of mailing lists compiled by LTSN.
   http://mathstore.ac.uk/etalk/index.shtml

Maths-Education  
   Email forum for those working in mathematics education to share ideas and experiences, and request information.
   http://lists.nottingham.ac.uk/mailman/listinfo/maths-education

Javamath-discuss  
   A general mailing list for discussion about mathematical software development in Java.
   http://lists.sourceforge.net/lists/listinfo/javamath-discuss

WebMath  
   A mailing list for those interested in mathematics on the World Wide Web.
   http://west.camel.math.ca/cgi-bin/wcms/webmath.pl

JISCmail  
   Mailing lists in mathematics and statistics for he UK academic community.
   http://www.jiscmail.ac.uk/mailinglists/category/Maths_&_Statistics.htm

Undernet Math  
   Topica email list serving the users of the IRC channel #math on the Undernet, for discussion and challenging puzzles.
   http://lists.topica.com/lists/undernet-math/

Mathforge  
   News and breakthroughs in the mathematical sciences, including software, education and books.
   http://mathforge.net/