For Emacs users, there's Gnus [1] and Newsticker [2]. Gnus doesn't support Atom feeds natively [3], so you have to call an external script to convert them to RSS before they're processed by Gnus. Newsticker supports RSS and Atom [4].

[1] https://www.gnu.org/software/emacs/manual/html_node/gnus/RSS...

[2] https://www.gnu.org/software/emacs/manual/html_mono/newstick...

[3] http://www.emacswiki.org/emacs/GnusRss

[4] http://www.emacswiki.org/emacs/NewsTicker