CataList: Catalog of LISTSERV Lists - L-Soft international, Inc.
From this page you can browse any of the approximately 30,000 public LISTSERV lists on the Internet, search for mailing lists of interest, and get information about LISTSERV host sites. This information is generated automatically from LISTSERV's LISTS database and is always up to date.
Tile.Net - List-Universe.com
A comprehensive Internet reference site for finding discussion lists (mailing lists); Usenet newsgroups; FTP sites; computer products and vendors; and Internet and Web design companies. Search mailing lists by keyword (algebra, calculus, etc.) to find information, including how to subscribe.