jQuery UI - Interactions and Widgets for the web
jQuery UI provides interactions like Drag and Drop and widgets like Autocomplete, Tabs and Slider and makes these as easy to use as jQuery itself.
If you want to use jQuery UI, go to jqueryui.com to get started. Or visit the Using jQuery UI Forum for discussions and questions.
If you are interested in helping developing jQuery UI, you are in the right place. To discuss development with team members and the community, visit the Developing jQuery UI Forum.
StealJS - A JavaScript build tool
The StealJS project is a collection of comamnd and client based JavaScript utilities that make building, packaging, sharing and consuming JavaScript applications easy.
For more information see this blog post and the (JavaScriptMVC forum entry)[http://forum.javascriptmvc.com/#topic/32525000000154003]