The jQuery Mega Select List is a plugin that converts large select lists into a mega-menu style list of options. This plugin doesn’t affect your form, posting back the selected value as if the options were being selected in a normal select list. You can animate the mega-select-list using CSS as per this example, or you can have it constantly expanded instead. You can set up the mega-select-list to allow single or multiple selections and in multiple mode can optionally limit the number of selections.
Tags: Mega Menu, MultiSelect