Here are some presentations that I've done in the line of duty:

Key Pages

W3C XML Activity

The W3C home page for XML

Tim Bray's Annotated XML Specification

The spec anotated by one of the authors. Juicy.

IBM's XML Page

I still have a soft spot in my heart for IBM.

XML.com

News articles, tutorials, and event announcements

Tools

Emacs

PSGML Mode

This is the best tool I've found for editing XML with some semantics.

tdtd Mode

An Emacs mode for editing DTD's.

Java

XML.apache.org

Your one stop open-source shop for XML on Java

Python

Python XML Package

This is the place