Sisyphus
Gmail-like client-side drafts and bit more. Plugin developed to save html forms data to LocalStorage to restore them after browser crashes, tabs closings and other disasters.
Zen Form
Add distraction mode for forms
Colorpicker
jQuery UI widget for color picking (similar to the one in Microsoft Office 2010).
jQuery Super Labels
Give your forms a helping of awesome!
jQuery.maskedinput
jQuery Masked Input Plugin
Formbuilder
[Needs Maintainer] Formbuilder is a small graphical interface for letting users build their own webforms.
jQuery Smart Auto Complete
AutoComplete plugin with smart defaults and flexibility to customize
Filereader.js
A lightweight wrapper for the JavaScript FileReader interface
Fancy Input
Makes typing in input fields fun with CSS3 effects
jQuery Validation
jQuery Validation Plugin
Validetta
A tiny jquery plugin for validate your forms
Starability
Accessible rating forms with cute animations on top.
H5F
A JavaScript library that allows you to use the HTML5 Forms chapters new field input types, attributes and constraint validation API in non-supporting browsers.
Tus Jquery Client
A jquery plugin implementing the tus resumable upload protocol.
Inputex
A javascript framework for YUI to build fields and forms.
jQuery Steps
A powerful jQuery wizard plugin that supports accessibility and HTML5.
Formvalidation
The best @jquery plugin to validate form fields. Designed to use with Bootstrap + Zurb Foundation + Pure + Semantic UI + UIKit + Your own frameworks. Star it. Try it. Buy it :)