Sams Teach Yourself HTML and CSS in 24 Hours (7th Edition)

Creating Graphics for the Web:

http://www.widearea.co.uk/designer/

The WDVL Style Guide:

http://www.wdvl.com/Authoring/Style/Guides/WDVL.html

Web Pages That Suck:

http://www.webpagesthatsuck.com/

HTML Help (Web Design Group):

http://www.htmlhelp.com/

Web Monkey:

http://webmonkey.wired.com/webmonkey/