4 links
Harley Hahn's Master List of Usenet Newsgroups
harley.com
Organized by topic (using entire words, not the cryptic abbreviations like "soc" or "std" sometimes used in newsgroup names).
news-admin.org
news-admin.org
Links to all known top-level hierarchies, any of which may register a subdomain of news-admin.org for their hierarchy.
Reference to Usenet Newsgroups from Tile.net
tile.net
Usenet newsgroups listed by hierarchy, description, and by index. No newsserver access. Each newsgroup has its own page with statistics and links to FAQs and other group informatio…
Usenet Info Center Launch Pad
ibiblio.org
Apparently no longer maintained, but of interest for historical reasons. Besides a list of Usenet newsgroups, also contains links to FAQs, newsgroup descriptions, and other Usenet …