Jquery-labeloverlay is a project mainly written in JavaScript, it's free.
jQuery Label Overlay - Takes care of hiding/showing labels that have been floated over the top of form fields.
Takes care of hiding/showing labels that have been floated over the top of form fields.
jQuery (tested with 1.4.2)
See examples.html
labelSelector
option allows you to tweak the CSS selector used to get the label for a particular field, is passed to $field.siblings()