PHP, XHTML, and a MySQL database.
PHP is probably the simplest language I've ever encountered. It has the ease of use of Java, without all the bloat, and it doesn't rely on any client side technologies (all it does is generate HTML). It also runs on a wider variety of servers than ASP (which is pretty much limited to IIS).
XHTML is just HTML with some stricter rules. I wouldn't really call CSS a programming language. It's more of a compliment to XHTML, allowing you to move the style information away form the code. If you need to brush up on XHTML and CSS, head over to the
w3schools site, they have a lot of nice tutorials.
I learned PHP over a few weeks with
this book. It's a little pricey (all O'Reilly books are

), but it's definitely worth the money, and it'll cover everything you'll need to do (connecting with a database mainly). If you want a preview, they have one on that site, you can see the index and the first few pages of each chapter.
You'll be able to write most of your pages in XHTML. PHP code can be inserted anywhere to make the page "dynamic".
For example.
CODE
<?php
$name_of_page = someFunctionToGetThePageName();
?>
<html>
<head>
<title><?php echo $name_of_page; ?></title>
</head>
<body>
<?php display_the_page(); ?>
</body>
</html>
And of course, your most important tool will be Google. Most PHP questions can be answered on PHP's website, and Google will find you those links if you ask nicely.
Happy coding.