This plugin takes all the immediate children of an element and makes two lists out of them.
The first list is those children containing a checked checkbox; the second list is those children containing an unchecked checkbox.
Children with no checkbox in them is your fault.
Next, each checkbox is hidden, and the lists are made sortable using jQuery UI.
Drag or double-click the item in the list to move it to the other list. Post your form as usual. Presto!