We mustn't forget about html editors such as
Notepad++ or
Quanta. (depending on the os)
Also a few links to html/css/javascript/etc. reference sites are necessary.
MSDN Library - Microsoft Technical Reference for html, css, and other scripting languages
w3.org is commonly linked, although I don't think it's very helpful
webmonkey - Tons of good tutorials for html, css, javascript, php, flash, and more
Dynamic Drive - free scripts to use in your site
Also,
Apache Friends - Set up an Apache, MySQL, PHP server on your own computer (easily). Either for testing before you upload, or for your actual server.