I am pretty sure that you know about Blogs, RSS & Atom feeds, etc..
Anyway, here is the summary, in case you want to forward to your friends.
A Web site that contains dated entries in reverse chronological order (most recent first) about a particular topic. Functioning as an online journal, blogs can be written by one person or a group of contributors. Entries contain commentary and links to other Web sites, and images as well as a search facility may also be included.(from answers.com)
You are reading a blog now!
RSS (Really Simple Syndication)
RSS is a Web content syndication XML format. (Syndication is a method of making content available to a range of outlets simultaneously). Most of the RSS feeds have a title, link and description.
RSS specification at RSS at Harvard Law
Atom is an XML-based document format that describes lists of related information known as “feeds”. Feeds are composed of a number of items, known as “entries”, each with an extensible set of attached metadata. For example, each entry has a title.
The primary use case that Atom addresses is the syndication of Web content such as Weblogs and news headlines to Web sites as well as directly to user agents.
OPML (Outline Processor Markup Language)
OPML is an XML format for outlines. The OPML specification defines an outline as a hierarchical, ordered list of arbitrary elements. The specification is fairly open which makes it suitable for many types of list data. It is most commonly used to exchange lists of RSS feeds between RSS aggregators or storing playlists.
Podcasting is a method of publishing audio broadcasts via the Internet. It allows users to subscribe to a feed of new files, usually MP3s. The word “podcasting” combines the words “broadcasting” and “iPod.”
The format used is RSS 2.0 with enclosures. Podcasting works like RSS, instead of reading the new content on a computer screen, you listen to the new content on an iPod or iPod-like device.
Like the enclosure of an email message, an RSS item enclosure is something big that may take a long time to download, or something binary that isn’t text you read. You can read the text that describes the enclosure, or the enclosure may somehow be related to the item.