Chosen is a jQuery plugin that makes long, unwieldy select boxes much more user-friendly.

Feature List:

• User Friendly

  Instead of forcing your users to scroll through a giant list of items, they can just start typing the name of the item they were looking for. Non-matching entries are removed from view and choices can be selected using enter or mouse click.

• Progressive Enhancement

  Because chosen replaces normal html select fields, you don't need to do anything special to make it work for browsers without JavaScript. You don't need to do anything special on the back end to handle the data either -- the form field still gets submitted as normal.