I hate these threads normally, however I thought I'd give this a go... There are a number of websites I spend a lot of time on because they're just so utterly usefull, obviously this forum is one of them, however I also understand that other people know of equally usefull sites that I dont know and vice versa...
This is the list so far:
http://www.w3schools.com - Excelent tutorials and reminders about HTML, CSS, Javascript and many more
http://msdn.microsoft.com (Although I cant use this anymore as my workplace has blocked all microsoft servers so that nobody can use MSN...) - Has excelent documentation for pretty much everything M$ supports, including HTML and Javascript.
http://www.yellowicon.com/ - Great source of free icons.
http://amazingtextures.com/ - Good source of free textures. Requires free registration for hires textures.
Anybody else? If a common URL comes up, I'll try to chuck it on this post.
EDIT: Mods - if you feel this is a waste of space, feel free to lock it - tis up to you.