Progression.js – Real-Time Hints & Progress Feedback For Forms
Progression.js is a jQuery plugin that shows tips about an active form field and also displays the progress (how much of the form is filled).
noUiSlider – Fantastic Range Slider For jQuery
noUiSlider is a Fantastic Range Slider For jQuery with support for single or double handles, custom starting values, vertical/horizontal orientation and the ability to get /set values.
Spectrum – Perfect jQuery Color Picker Plugin
Spectrum is a jQuery colorpicker plugin that probably comes with all the features you are looking for. It is image-free (only CSS and JS) and can be used for all browsers or only as a polyfill for the input[type=color] of HTML5.
Typeahead.js – A jQuery Autocomplete Plugin By Twitter
Typeahead.js for building smart auto-complete form fields comes as a jQuery plugin, shows suggestion as-users-type and can feature top suggestions with the help of styling.
Dropzone.js – Drag and Drop File Uploads
Dropzone.js is a JavaScript library that simplifies creating a drag and drop file upload functionality.
