QuiteRSS is a desktop news feeds (RSS/Atom) reader with a Qt interface. It's both fast and convenient to use, embeds a WebKit view, allows searching, bookmarking and filtering feed items or users. QuiteRSS also includes ad blocking, proxy support, feed update timers, a tree-grouped feed list, sound and visual notifications, OPML imports, and is fully portable.
Thunderbird is a desktop mail client. It's a companion product to Mozilla Firefox. Besides standard email, it supports newsgroups, feed reading, and chat protocols (XMPP, IRC and Twitter), all with multiple identities or accounts. Through Mozilla Lighning or other plugins it's extensible into a full personal information manager. Out of the box it supports SMTP, POP3, IMAP, SSL/TLS, S/MIME, LDAP, RSS/Atom, and searching, filtering or grouping, labels, virtual folders, and comes with a spam filter
Sismics Reader is web-based RSS/Atom news feed aggregator implemented. It has an AJAX-powered UI, a mobile view, provides OPML import and export, and a search function. It's distributed as Java WAR file and comes prepackaged for multiple plattforms.