Stunningly good resource for finding mailing lists. Searches bring up a list of matching mailing lists with one-line descriptions and hotlinks for more information or to subscribe. Superb!
Bob and Varda Novick operate this fantastic site with everything you want to know about every kind of mailing list and links to all the resources you could want. Excellent!
Another searchable catalog of mailing list descriptions. The advantage of using this one is all results are output on one long page including descriptions of the lists and how to subscribe.
Listserv only. Another resource for finding mailing lists run on Listserv software. 9000 groups. Several ways to search. One nice feature: it tells you how many subscribers each list has!
Nice, searchable list of mailing lists (originally compiled by Rich Zellich). Vivian is the author of Internet Mailing Lists Navigator from Prentice Hall.
Stephanie da Silva's "Publicly Accessible Mailing Lists" web site has mailing list descriptions cross-referenced by name and subject. Updated once a month.
Rob Kabacoff at Inter-Links has set up this very good resource center for finding online mailing lists. Includes links to *five* mailing list directories, plus common list commands and tips for using mailing lists. Nice resource.