World Wide Web Consortium
The W3C was created in October 1994 to develop common protocols (HTTP, etc.) and web authoring languages (HTML, CSS, XHTML, etc.) that promote the evolution of web standards and the interoperability of web pages now and into the future.

The Web Standards Project
The WaSP is a grassroots coalition of web developers and enthusiasts founded in 1998 to promote the accessibility and long-term viability of any site published on the Web. WaSP works with browser makers, authoring-tool makers, and webmasters to help deliver these standards to developers and users alike.

Browser Upgrade Campaign
This WaSP-initiated campaign provides information for upgrading to web browsing software that is compliant with current web standards.

Producing Valid Code in Dreamweaver MX
A comprehensive article at the Macromedia Application Development Center on producing clean, valid code in Dreamweaver MX and the adjustments needed to develop sites under the new XHTML standards.

Fixing Your Site with the Right DOCTYPE
DOCTYPEs (short for document type definition) are essential to the proper rendering and functioning of web documents in standards-compliant browsers such as IE6/Win, IE5/Mac, and Mozilla. They are also required for code validation through W3C. This excellent article explains DOCTYPEs and lists some you can use. (Dreamweaver 4, by default, does not include DOCTYPE in new pages; this oversight has been corrected in Dreamweaver MX.)