XML is a set of rules for encoding documents in machine-readable form. It is defined in the XML 1.0 Specification produced by the W3C, and several other related specifications, all gratis open standards.
[HD] How to write a simple XML document: Tutorial
Just Enough XML to Survive
Learn XML in 4 Minutes
Eric Explains: XML
Convert Excel Spreadsheet data to XML
DrC and Rollo: What is XML?
XML
Flash CS4: Complete Flash XML Gallery Tutorial AS 3.0