Select

Bootstrap Dual Listbox is a responsive dual listbox widget optimized for Twitter Bootstrap. It works on all modern browsers and on touch devices.  

multi-select.js is a user-friendlier drop-in replacement for the standard <select> with multiple attribute activated.   multi-select.js - Features: Free (under WTFPL license) Works in an unobtrusive fashion Fully open sourced Keyboard support Provides some callbacks Fully customizable via CSS Depends on jQuery 1.8+ Tiny code ~8kb minified  

jQuery Cascading Dropdown is a simple and lighweight jQuery plugin for creating cascading dropdowns. You can set the default selected dropdown item in a dynamic dropdown scenario and combine both static and dynamic dropdowns.  

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

Validetta is jQuery plugin which you can do client-side validation of your forms. It aims to decrease your burden with easy usage and flexible structure.    Validetta - Features: You can check fields whether it is empty or not or it is chosen or not. You can do e-mail check. You can do number check. You can check if the two fields are equal to each other. You can check credit card number validation. You can limit number of characters written to fields. You can limit number of choice of

Selectric is a jQuery plugin designed to help at stylizing and manipulating HTML selects   Selectric - Features: Keyboard navigation (Up/Down/Left/Right/Word search) Easily customizable Pretty lightweight (3,5KB minified and less than 2KB minified/gzip) Options box always stay visible Doesn't rely on external libraries (besides jQuery) Word search works with western latin characters set (e.g.: á, ñ, ç...)    

Multiple select is a jQuery plugin to select multiple elements with checkboxes :). Multiple select - Features: Default option allows to show checkbox. Ability to grouping elements. Supports to show multiple items in single row. Select all options. Feature to show placeholder.    

Selectize is the hybrid of a textbox and <select> box. It's jQuery-based and it's useful for tagging, contact lists, country selectors, and so on.   Selectize.js - Features: Skinnable — Comes with LESS stylesheets and shims for Bootstrap 2 and Bootstrap 3 (+ precompiled CSS). Clean API & Code + Extensible — Interface & make addons like a boss with the plugin system. Fully documented on GitHub & inline. Smart Ranking / Multi-Property Searching & Sorting — Want to search

HeapBox is an HTML selectbox replacement powered by jQuery. It keeps mappings to source selectboxes, which means you can use HeapBox and your POST/GET form requests together.    

Fancyform is a tool that offers a nice and elegant way to transform your HTML elements into custom styled elements. It is build on the Javascript framework jQuery and is easy to implement and customize. The elements you can style are input:radio, input:checkbox, select and textarea.