Cool Stuff
Nice example: http://www.nytimes.com/interactive/2012/10/15/us/politics/swing-history.html
JS Playground to test CSS&HTML&JavaScript
Does your website pass the browser test?
JavaScript charts
http://dygraphs.com/index.html
Simple charts - open source not fancy
http://www.highcharts.com/products/highcharts
Free for non-commercial
Mixture of charts
http://www.amcharts.com/javascript-charts/
Maps and charts
http://www.zingchart.com/js-charts
Charts, maps, word cloud
http://www.jqwidgets.com/jquery-widgets-demo/
Free for non-commercial
Mixture of simple UI controls
http://www.jscharts.com/examples
Simple charts - free to use with watermark
Simple
http://www.fusioncharts.com/explore/charts/
Charts and Dashboards
http://gojs.net/latest/samples/index.html
Lots of different tree structures, mind maps, flow charts, org charts etc
https://google-developers.appspot.com/chart/interactive/docs/gallery
Google has a go at it
http://canvasjs.com/html5-javascript-column-chart/
Charts (including candlestick and bubble)
More than just charts, whole dashboards
http://js.devexpress.com/WebDevelopment/Charts/
Charts, maps, Gauges
http://www.anychart.com/products/anychart7/gallery/
Clean & simple (Oracle partner)
JS Frameworks
Most well known JS library (MIT license)
(Testing Framework: http://qunitjs.com )
https://docs.angularjs.org/misc/faq
Angular JS (Google)
Nice: bidirectional data binding
http://knockoutjs.com/index.html
Opensource (MIT license)
https://saucelabs.com/javascript/
Another tool to Test your Javascript