I discovered, via the xml-dev mailing list, that Gmane [0] provides NNTP gateways (i.e., Usenet) for some number of mailing lists.
Among these are some Ruby mailing lists:

news://news.gmane.org/gmane.comp.lang.ruby.documentation  (ruby-doc)
news://news.gmane.org/gmane.comp.lang.ruby.german
news://news.gmane.org/gmane.comp.lang.ruby.cvs
news://news.gmane.org/gmane.comp.lang.ruby.core     (ruby-core)
news://news.gmane.org/gmane.comp.lang.ruby.general    (ruby-talk)



[0] www.gmane.org


 James Britt
http://www.jamesbritt.com
http://www.rubyxml.com
http://www.ruby-doc.org