phillyfuture.org makes extensive use of feed and syndication to list area weblogs. It's important that you understand what these are, and make sure your website can provide them in order to be listed!
The following is from the website FaganFinder. You can find more detailed information about feeds, RSS Aggregators, and subscribing to feeds, there. Additional thanks should go to Pittsburgh Webloggers for finding this concise description.
What is RSS?
Before you go any further, realize this: RSS is really simple. Just because it is an acronym doesn't mean that it's complicated. Don't get scared away, there's really nothing to it. I said it was an acronym, but depending on who you ask and what version of RSS you are speaking about, it may stand for Really Simple Syndication, Rich Site Summary, RDF Site Summary, or a variation on one of those. None of that matters to you anyhow. Another thing that you don't need to care about is the versions. There are 0.90 and 0.91 (created by Netscape), 1.0 (by RSS-DEV), and 0.9x and 2.0 (by UserLand Software) versions, but almost all applications that handle RSS feeds can read all the different versions.
When a website has an RSS feed, it is said to be syndicated. There are various other syndication formats besides RSS (such as Atom), but RSS is by far the most widely used and supported today. RSS files do not have a common file extension, although they frequently end in one of .xml, .rss, or .rdf(note that other extensions may be used also). The term 'scraping' refers to creating an RSS feed for a website that doesn't provide one itself (i.e. scraping the text off of the page). That is, scraped feeds are not created by the same people who created the content within the feed. Scraped RSS feeds may stop working if the page changes its layout.
What is Atom?
Atom is a format quite similar to RSS. It was created by people who felt that RSS could be improved upon, and some that disagreed with some of the politics regarding RSS. Some people are heavily involved in the (quite unimportant, in my opinion) argument as to which format is better. The Atom format is in development, but as of February 2004, Atom version 0.3 is stable. There are pros and cons to the format, but that's more complex than I am going to deal with here. The basic difference is that while Atom is somewhat more complex (for producers of Atom feeds), it is also able to carry more complex information, and it is consistent across the syndication, storage, and editing of information. Just about everything on this page which discusses RSS applies equally well to Atom. You can learn more about Atom at the official website, AtomEnabled.org.
What is OPML?
OPML is an XML format for outlines. You can read more about it on the OPML website. An OPML file can be made that lists all the RSS feeds you subscribe to, and this can be very useful. Many RSS aggregators can produce (export) OPML files, and many can read (import from) them. This is a very useful feature. Suppose that you are using aggregator ABC to read 50 RSS feeds. Your friend tells you that aggregator XYZ is so much better than ABC, so you want to try it out. Rather than re-subscribing to all 50 feeds from XYZ, you can export an OPML file from ABC, and import that file into XYZ, assuming that both aggregators have these features. Many people put their OPML files online, which would allow you to instantly to subscribe to all the feeds that they read. Share Your OPML is one website that makes use of information from many people's OPML files.