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.
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.
Select2 Bootstrap CSS is a simple css to make select2 widgets fit in with Bootstrap.
Select Multiple is an user-friendly drop-in replacement for the standard select with multiple attribute activated.
Combo Select is a jQuery plugin that converts a select box into a searchable and keyboard friendly interface. Fallbacks to native select on mobile and ipad devices.
Selectivity.js is a modular and lightweight selection library for jQuery and Zepto.js.
Zelect is a jQuery plugin to create custom
SumoSelect is a jQuery single/multi select plugin which can be used on almost any device. It can be fully customizable using simple css properties.
Select3 is a modular and lightweight selection library for jQuery and Zepto.js
Selectator is a jQuery-based replacement for select boxes. It supports searching, and affects the original select box directly, which is used as the data container.