[zim2411]

Hm... a decent list, but it's a little outdated. I would avoid dynamicdrive.com now, most of their scripts are ancient, and kind of trashy. Avoid ASP like the plague.

Javascript Tools:

• http://jquery.com/
• http://jqueryui.com/
• http://jquerymobile.com/
• Unfortunately, jQuery has taken their plugins site offline, so you have to Google around to find things
• Modernizr - Brings conditional logic to your CSS and allows you to target browsers by feature sets

Design Discussion

• http://www.smashingmagazine.com/ - Excellent resource, lots of user experience articles. If you really want to pursue web design/development, start reading this now.
• http://css-tricks.com/

Both of those sites feature responsive design. Resize your browser, and watch how the contents of the page realign so that you never have to scroll horizontally. You will definitely get bonus points if you can do this on your site.

CSS

• LESS CSS - Write less CSS code. This is awesome, but be sure to compile your CSS for your production site.
• Sass - Similar to LESS, lets you write CSS more efficiently.
• CSS3 Gradient Editor - Take advantage of CSS3's linear gradients to render nice things in-browser
• CSS3 Info - More CSS3 information including box-shadows, rounded corners, rgba, and more.
• Article about using SVG instead of CSS3 Gradients - You have to use SVG for IE9, unfortunately
• CSS3 Buttons - A nice variety of good looking buttons
  

Testing

• Browsershots - Get screenshots from just about every browser possible
• Expression Web SuperPreview - Preview what a page looks like in IE6, 7, and 8 on newer computers. Limited functionality though, as you can't really interact with the page.
• Microsoft's Internet Explorer Virtual Machines - Test in older IE versions in a virtual machine. You can use the developer tools to debug things.

Misc.

• Bootstrap - A frontend framework for responsive design sites
• HTML5 Boilerplate - Excellent starting point for doing a page from scratch. Use this.
• Firebug - The best DOM inspector (in my opinion.) If you do not know about DOM inspectors yet, learn NOW. They are your most powerful debugging tool. Chrome, Safari, and even Internet Explorer ship with DOM inspectors. Firefox has a new one, but it's not nearly as powerful as Firebug.