The resources below are loosely ordered from beginner to expert. All of them have give me something to think about.
w3schools was really the first introduction I had to web programming. Much of the material is out of date, but the quantity and diversity of the tutorials provided more than makes up for it. Each tutorial comes with a quiz, so you can make sure your eyes didn't glaze over during the process. I find it a great reference for quickly getting a start or just refreshing my mind, even if the examples are not exactly idiomatic for modern development.
When my mind tires of trying to remember my vim commands, I usually do my text editing in notepad++. Syntax highlighting for more languages than I can list is built in, as well as a tabbed layout. Notepad++ is a very responsive and light weight solution for such a fully featured text editor. I make heavy use of it at home and work.
Chrome Developer Tools
Internet Explorer Developer Tools
Liked the live editing in the developer tools, but want a lighter weight tool for prototyping or the ability to easily share? Enter jsFiddle, a tool that shows html, css, and js files all on one page. A number of scripting libraries are quickly included under the panel on the right, rendered pages appear on the bottom right. Save your file and the URL changes to a link you can share with anyone, allowing them to edit and fork your work.
Tired of manipulating DOM elements? Start drawing. The HTML5 Canvas element let's you go nuts with creativity. You've probably already seen what it can do on the Google home screen and plenty of games are now giving it a shot. If you need some graphical splash in your app, Canvas is a good tool to research.
Trello Tech Stack
Not convinced that all of this fancy new tech can be used to build real software? Heard of FogBugz, Fog Creek Software, or Joel Spolsky? If you haven't go search, I'll wait.
No seriously go look them up if you don't, it is more important than this article.
Now that you know I'm about to make an argument from authority. Check out the link above on the Tech Stack for Fog Creek's new product Trello. This is a massively scalable freemium web app, built on Backbone and Node.js. It is expected to be a substantial part of Fog Creek's business in the future.