jQuery UI - Interactions and widgets for the web
jQuery UI provides interaction like Drag and Drop and widgets like Autocomplete, Tabs and Slider.
If you want to use jQuery UI, goto http://jqueryui.com to get started.
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 http://forum.jquery.com/developing-jquery-ui.