Codecube - DHTML
Four articles covering the JavaScript API and layout.

Communicator DHTML Documentation
How to use Dynamic HTML to incorporate style sheets, positioned content, and downloadable fonts in your web pages.

Developer Shed - DHTML
Several tutorials, including an introduction to the Document Object Model.

DHTML Kitchen: Master Series DHTML
Detailed explanations of current coding standards and principles. Accessibility issues and solutions to cross-platform and cross-browser incompatibilities, including for Opera and Mac IE are noted and discussed.

DHTML Lab
Biweekly how-to column.

DHTML School
Award winning, well organized, and easy to understand tutorial with lots of working examples and source code.

WebDeveloper.com - DHTML
A DHTML primer.