Style Guide and Helpful Tutorials All In One
The NYPL Style Guide explains in simple terms the basics of XHTML, CSS, why they matter, and how to use them. There are authoring tips and tools, lots of samples, style sheets, transitioning from HTML to XHTML, working with Dreamweaver, XHTML accessibility tips, CSS guidelines, and more. And this is only Phase I of this Style Guide. I can hardly wait to see more!
[link via Zeldman]