3 pages found in Newsgroup Directories:
Google Groups' Directory
Usenet newsgroups and Google Group mailing lists classified by topic, language, region and activity.
based browsing of the groups.
Usenet Info Center Launch Pad
Apparently no longer maintained, but of interest for historical reasons.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 information.