I heard a rumor that Aptana is a great editor for JavaScript. I haven't tried it, but Rick Strahl likes it, which is a good kudo in my book. Editing JavaScript in Visual Studio is "okay," not great, so I welcome a better editor.

Aptana's site also has a bunch of great video tutorials, for those of you who want webcasts.

Aptana Screenshots

"Code Assist" (Intellisense) for JavaScript, CSS, & HTML:
  

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