knockoutJs wrapper for Eric Hynd's jQuery UI MultiSelect Widget. Please see his site for more details: http://www.erichynds.com/jquery/jquery-ui-multiselect-widget/
Here is a fiddle: http://jsfiddle.net/ericpanorel/Rre2s/
If you don't know what knockoutJs is, head over to: http://knockoutjs.com/