Dolly.js

Simple jQuery UI widget that adds spreadsheet-like cell cloning capabilities to HTML tables.

Decoy

jQuery plugin to make decoys for your elements.

Double

Double is a jQuery plugin for hiring doubles for your elements.

jQuery CloneYa

jQuery plugin for cloning elements in a nested manner

jQuery Clonebox

Simple solution for cloning input boxes, with convenient ‘add/remove buttons

jQuery autofill

jQuery plugin for autofilling text input fields from another text input fields.