Ergo Menu is a jQuery dropdown menu plugin that takes a regular UL
list and transforms it into either an expanding menu, or standard dropdown menu.
Dropdown is a lightweight jQuery dropdown plugin that supports key/value search and has multiple selection option.
Select2 Cascade is a jQuery plugin to create cascading /dependent select list by using Select2 - one of the most popular select list plugin.
multi.js is a user-friendly replacement for select boxes with the multiple attribute. It is mobile-friendly, easy to use, and provides search functionality. multi.js is also easy to customize and style with CSS.
vDrop is a minimalistic and customisable jQuery plugin to replace standard HTML select dropdowns.
Pretty Dropdowns is a simple, lightweight jQuery plugin that converts <select>
drop-down menus into "pretty" menus that you can style using CSS. As an extra bonus, it does its best to keep the menu options within the viewport.
Choices.js is a lightweight, configurable selectbox / text input plugin. Similar to Select2 and Selectize.
With Simple Select you can create custom styled select elements by using css and jQuery.
Nice Select is a lightweight jQuery plugin that replaces native select elements with customizable dropdowns.
Searchable Option List is a jQuery plugin which enhances your <select>
HTML elements and makes the options searchable. It works for regular option lists as well as those marked as multiple
Quick[select] is a jQuery plugin for quick selection of common options in select boxes. Quick[select] uses the browser's native select list for its overflow, meaning it will work great on all devices.
A tutorial about creating custom select elements with unique style. It's created by using jQuery and CSS.
A tutorial about creating custom select box by using css and jQuery.
Bootstrap Chosen is an alternate stylesheet for Chosen. This one is supposed to integrate better with Bootstrap 3.0.
Select2 Bootstrap CSS is a simple css to make select2 widgets fit in with Bootstrap.