Please check out the new NewsReaderssm discussion forums available via web browser or newsreader GUBA: Gigantic Usenet Binary Archive offers a paid service to view newsgroup files via your web browser.
Webmasters
can sign up to refer customers to GUBA!
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Newsgrouphosting.com from Mutant Penguin Software, the makers of MPNews server! "With our integrated NNTP newsgroups, web forum and blog system, everyone can choose the way to interact with your community that suits them best.
You have full control over your newsgroups, with powerful access control systems to limit access to particular newsgroups, automatic filtering to keep your newsgroups clear of unwanted messages, options to review messages before they are posted or to delete them afterwards, and much more."
Lugnet (Lego Users Group) is an excellent example. Users can read/post via nntp client, e-mail, or web interface, and thus can use whatever is most comfortable or convenient (or even use news most often, but use the web interface when on the road, etc.). Also shows use of registration to gain access to the nntp (and web and e-mail) group.
If you wish to run a private group or groups, you can run your own news server (see other sections of this site), or see the Newsfeeds page for companies that might host private groups. In particular:
Newsville.com indicates that they provide such service.
Company (link to page about newsgroups, if exists)