FermatNumbers  
   A group for aggregating all the known properties of Fermat Numbers F(m)=2^2^m+1 in one place. Links to distributed search and lists. Archive available to non-members.
   http://groups.yahoo.com/group/FermatNumbers/

goldbach  
   Discussion list for the Goldbach Conjecture.
   http://groups.yahoo.com/group/goldbach/

numbertheory  
   Mailing list covering recreational and serious aspects. [Requires free Yahoo membership.]
   http://groups.yahoo.com/group/numbertheory

PrimeForm  
   Discussion group for the primality-testing program, PrimeForm. Includes links to the PrimeForm program's home page, contact and download information.
   http://groups.yahoo.com/group/primeform/

Primenumbers  
   Discussion list for those who enjoy prime numbers, primality testing, and closely related subjects.
   http://groups.yahoo.com/group/primenumbers/

SeqFan Mailing List  
   Devoted to the study of integer sequences.
   http://www.ccr.jussieu.fr/gmpib/seqfan/

Archives of Number Theory List  
   Archives of postings to the Number Theory mailing list (NMBRTHRY).
   http://listserv.nodak.edu/archives/nmbrthry.html

Somos Sequence Mailing List Archive  
   Maintained by Jim Propp.
   http://www.math.wisc.edu/~propp/bilinear/archive