XML

World Wide Consortium (W3C)
The organistation who wrote the XML specification. You can download a copy of the XML specification, available in HTML, PDF, and .txt formats.

Webmonkey
Includes an easy to follow overview of XML and XSL (the stylesheet language for XML).

What is XML (Builder)

What do XML documents look like? (XML.com, Oct. 3, 1998)

Why should I use XML instead of HTML? (XML.com)

Where can I get an XML browser? (XML.com)

Is there an XML version of HTML? (XML.com)

Do I have to switch from SGML or HTML to XML? (XML.com)

What about XSL? (XML.com)

XML Validation Service (XML.com)