First of all, we may disable dragging mouse:
Delete "_mouseDrag" function in your jquery-ui.js for “selectable” part.

Now we may write the code for our selectable object:

1. var xselect;
   $(function() {
     $("#yourselectable").selectable({
       selecting: function() { //here we will make unselected the last chosen item
         if ( xselect && xselect.length > 0 ) {
           $(xselect[0]).removeClass("ui-selected");
         }
       },
       selected: function () {
         xselect = $("#selectable1").children(".ui-selected"); //keep the selected in a variable
         $("#selectable1").children(".ui-selected").removeClass("ui-selected"); //make all unselected
         $(xselect).addClass("ui-selected"); //chose the selected object       //and some code… that you may record this xselect object’s id, etc…
         //I am giving an example anyway
         $(".ui-selected").each( function() {
           cid = $(this).attr("id"); //selected object’s id is in "cid" now
         });
       }
     });
   });
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   
   

For more information you can see my detailed post here;
http://farkow.com/2010/05/jquery-ui-single-selectable