If you want a template-driven site, go for Joomla, Drupal, Mambo etc. unless you want to design your templates from scratch - could be daunting if you do not have a background in design/dev. However, I would suggest this route as you get what you want (with a little blood, sweat and tears). The CMS route gives you what THEY think is a good template. You want everything for free? Well, forget Adobe/Macromedia products then (I'm ashamed to say that I still use Dreamweaver MX for little projects). You'll need a good text-editor and very little else. Well, here's my list of free stuff - although some can be said to be feature-lacking rather than feature-rich!
Texteditor: Notepad++ (my editor of choice, but there are hundreds out there)
IDE: Aptana, Netbeans (I don't tend to use them very often - but they are very useful)
FTP Client: CoffeeCup, FireFTP for Firefox
Graphics: Gimp 2 (feature rich)
Browsers: IE, Chrome, Safari, Firefox, Opera (if using Linux, Konqueror as well). If you can't install all these browsers for whatever reason, try 'browsershots'.
Apache/pHp/MySQL: XAMPP - my favourite installer/package
SQLyog - an easy to use GUI for MySQL
Testing tools: HTML and CSS validators from W3C. cynthiasays.com is useful for Section508/WCAG.
Remember that just because your site passes these tests, doesn't mean that it will, be visually enticing, be accessible or be any good!