I tried this setting:
(setq gnus-select-method '(nnml "comp.lang.lisp"))
But when I activate Gnus, no grouop is shown. How do I add groups like comp.lang.*?
Edit: I tried with nntp:
(setq gnus-select-method '(nntp "comp.lang.lisp"))
but it doesn't work:
Warning: Opening nntp server on comp.lang.lisp...failed: ; Server nntp+comp.lang.lisp previously determined to be down; not retrying
Expanding on @logoscia's comment, comp.lang.lisp isn't an NNTP server, but a newsgroup. You can use Gmane/Gwene to read mailing lists and RSS feeds via NNTP. You can also add a traditional news server, like news.eternal-september.org. The elisp snippet below can get you started.
(setq gnus-select-method '(nnml "")) ;; this depends on how you want
;; to get your mail
(setq gnus-secondary-select-methods '((nntp "news.gmane.org")
(nntp "news.eternal-september.org")))
Start Gnus with M-x gnus. In the group buffer hit ^ to get to the *Server* buffer then browse the newsgroups on the servers. From there you can subscribe/unsubscribe to newsgroups with u. Back in the *Group* buffer you will see your subscribed groups. For details, see the Gnus manual.