Links 
Web Design
General Design
Jeffrey Zeldman Presents: The Daily Report and much else about high-quality Web design. I complained about a site he had designed without knowing that he had designed it and received a rebuttal e-mail from a web celebrity who still finds time to respond to piddling complaints.
Useit.com: Jakob Nielsen says, in however many words it takes for everybody to listen to him, ‘keep it simple and make the web usable.’ His biweekly Alertbox column on web usability
Web Page Design For Designers emphasizes the realities of design, recommending the use of tables and hard spaces as well as Cascading Style Sheets; also, one should look at the site just to take in the aesthetic design of its own pages.
Viewable With Any Browser needs to be every designer’s creed. This site also has a design guide.
HTML, XHTML
Bare Bones Guide to HTML lists all those tags and tells you what they do.
Web Accessibility Initiative of the W3C.
Validator for XHTML from the W3C.
Anabella’s HTML help shows you how to do the simple and essential HTML things.
Composing Good HTML sounds like a good thing to do.
HTML Goodies can be useful; it covers some things pretty well and many things not at all.
HTML Document Character Set: the “Annotated Table of Characters” from horizontal tab to yin yang.
CSS Tutorial from Style Master CSS editor.
PHP
Dealing with forms (PHP.net tutorial)
Send e-mail from a web form. (Note: at one of my sites the variables were not received by the PHP in $_POST[input_field_name] and instead worked simply as $input_field_name.)
PHP and SQL timekeeping sample.
Databases
General Design
Databases from scratch is an excellent introduction.
SQL
Introduction to Structured Query Language by James Hoffman is more than a complete reference to SQL.
MySQL tutorials at Developer Shed.
Pal’s Linux RDBMS Library covers Relational Database Management Systems in the abstract, in forms such as MySQL, as well as on Linux. A lot of this stuff isn’t exactly for beginners.
Fonts and Graphics
MyFonts has good prices on just about any font out there and lets you display any text you want in any size you want, creating very useful GIFs for web page titles and the like.
Fontastic! free fonts by friendly font designers.