Specifications

Mod_enclosures Proposal
Proposal of enclosures support for RSS 1.0 (as module) and RSS 2.0. [PDF]
http://www.crocodile.org/lord/RSSenclosures/RSSenclosures.pdf

Open Content Syndication Directory Format
Open Content Syndication is an XML format for describing channel listings, including RSS files.
http://internetalchemy.org/ocs/directory.html

RSS 0.90
DEPRECATED: A copy of the original Netscape version of the RSS0.90 specification. This is no longer in use, and is here for historical reasons only.
http://www.purplepages.ie/RSS/netscape/rss0.90.html

RSS 0.91
DEPRECATED. Description of RSS current practice. By Dave Winer, UserLand.
http://backend.userland.com/rss091

RSS 0.92
DEPRECATED. The Userland specification of RSS0.92 - by Dave Winer, December 25 2000
http://backend.userland.com/rss092

RSS 0.93
DEPRECATED. A abandoned upgrade of the Userland specification of RSS0.93 - by Dave Winer, April 20 2001
http://backend.userland.com/rss093

RSS 1.0
The latest "Complex RSS" specification. As created by the members of RSS-DEV. It extends RSS with RDF-style metadata, and modules.
http://web.resource.org/rss/1.0/

RSS 1.1
Draft of RSS 1.1 standard, a proposed replacement to RSS 1.0.
http://inamidst.com/rss1.1/

RSS 2.0
The latest "Simple RSS" specification - following on from 0.93, and not including RDF
http://blogs.law.harvard.edu/tech/rss

RSS 2.0 Specification (version 2.0.8)
The current Really Simple Syndication 2.0 specification, published by the RSS Advisory Board.
http://www.rssboard.org/rss-specification

rss-dev
The email list for the RSS interest and working groups, discussing the present and future of the RSS format, as well as working on uses and development. Responsible for RSS1.0
http://tech.groups.yahoo.com/group/rss-dev/

Diveintomark - The Myth of RSS Compatibility
"There are 9 versions of RSS, all of which are incompatible with various other versions." Describes the 9 versions and gives examples of the incompatibility issues. <small>(February 4, 2004)</small>
http://diveintomark.org/archives/2004/02/04/incompatible-rss

RSS 1.0: The New Syndication Format
Background on the RSS 1.0 Spec. By Jonathan Eisenzopf, Web Reference. <small>(August 15, 2000)</small>
http://www.webreference.com/perl/tutorial/rss1/