A List Apart: Rated XHTML
Article by Peter-Paul Koch: "XHTML isn't about the present, it's about the future."
About - What is XHTML?
An article explaining XHTML in relation to XML and HTML.
W3C: XHTML 1.0 Press Release
The World Wide Web Consortium's official press release for XHTML 1.0.
WebReview: XHTML - Our Last, Best Hope for Clean C
Article about the need for XHTML and the differences from HTML.
XHTML: HTML Merges With XML
Article from Dev.x WebBuilder, outlining XHTML.
XML.com - XHTML: Three Namespaces or One?
Discussion into the three DTDs of XHTML.