KnockoutJS is very interesting framework, it uses MVVM pattern, very similar to our desktop.
Underscore, it is battery to enhance the basic library for JS.
Jscex, it is one open source project from Zhaojie, and its feature looks like “Async/Await” in Dotnet 4.5
Mozilla developer center, most good resource center for JS developer
jsFiddle, try to write code online
NodeJS, use JS in server side, it could use with IIS and Windows Azure cloud.