Thank you for not using Internet Explorer

HTML/PHP links

Mozilla/Netscape 6+ Sidebars Handy Sidebars for HTML and CSS Quick Reference
XChat Great irc client for Linux and Windows.
PHP site Excellent resource for anything PHP.
HTML Validation Service Validate any site. Also CSS validation

Linux and related stuff

Spamassassin eats spam (the e-mail kind).
LinuxTodayNews site for Linux related news.

DigitalSpy UK Based site for all things TV - including good forums on DTT (FreeView)
Asia Pacific FTA Sat TV Guide
Play.com Great place for Region 1 and 2 dvd's.

Aardvark Commentary from Bruce Simpson. Updated daily - worth a read.
The Register