Rich Site Summary (RSS) is a data format that allows computers to exchange files containing summaries of stories. Each story typically has a title, location, and possibly a brief synopsis. RSS is extremely simple, and is expressed using standards-defined Extensible Markup Language (XML). Thousands of blogs and other web sites all over the Net produce RSS files describing their content.
The cool thing about RSS is that it's easy to write a program to produce or manipulate the data in an RSS document. RSS is so simple to generate and manipulate that hundreds of programmers have written tools to exploit the thousands of RSS feeds on the Internet.
For example, the Mac OS X toolbar application called MacReporter (http://inferiis.com/products/macreporter/) can regularly fetch headlines from news sites and blogs. You can then scan the headlines looking for interesting news to blog or simply read. Meerkat (http://meerkat.oreillynet.com) is an excellent web-based RSS reader that allows you to filter the feeds you receive by keyword, time, and origin.
Some bloggers have coded custom RSS tools that integrate tightly with their blogs, so that filtered headlines from other sites appear in sidebars on their front pages.
Dave Winer's Weblogs.com is a list of blogs that have sent an "updated" notice over the Internet to the service. If you're looking for a list of recently updated weblogs, you can visit http://www.weblogs.com and browse the list; but if you're a programmer, you can fetch the Weblogs.com RSS feed and get an easy-to-manipulate list of recently updated sites to feed to a search engine or RSS reader.
RSS is a powerful way of spreading your blog entries far and wide.
Some blogging tools, such as Radio and Movable Type, publish RSS feeds by default. Others have options to enable feeds. If your blogging tool doesn't generate its own feed, you can still publish blogs by using Julian Bond's RSSify tool at http://www.voidstar.com/rssify.php.
Most blogs that offer RSS feeds have links to those feeds on their sites. A new technique that's gaining popularity is to embed in your web page a pointer to the RSS for that page. This makes it much easier to write tools that automatically discover RSS feeds.
An RSS aggregator is a tool that regularly fetches RSS feeds and stores their contents in a database. A personal aggregator (such as Plucky, available at http://geoffreygrosenbach.com/plucky.html, or AmphetaDesk, available at http://www.amphetadesk.com) is used as a kind of software agent, a tool that searches any RSS feed you specify for stories, filters them according to your preferences, and displays the results.
Some blogging tools, such as Radio UserLand, include aggregators. You can fetch and filter RSS feeds from all over the Internet, from blogs to major news-organs such as the New York Times, which has a special arrangement with UserLand Spftware to provide Radio UserLand users with exclusive news-feeds. Radio UserLand's aggregator makes it trivial to turn stories that you discover via RSS into blog entries, by ticking a box and adding some commentary.
Internet aggregators such as Meerkat fetch thousands of feeds and make them available to people and to software agents.
Syndic8 (http://www.syndic8.com) and NewsIsFree (http://www.newsisfree.com) maintain giant master-lists of thousands of feeds that can be downloaded and imported into personal aggregators. Both sites allow you to submit your own RSS feed for inclusion on the master-list.