jQuery plugin: ‘autoResize’ - James Padolsey
http://james.padolsey.com/javascript/jquery-plugin-autoresize/

jQuery plugin: ‘autoResize’

I remember googling for something of this nature a while ago but all I found were countless attempts using the cols and/or rows attribute of the textarea, thus making it pretty useless if you weren’t using a fixed-width font. Inspired by Jason Frame’s method, I’ve created an animating ‘autoResize’ jQuery plugin. Although it was inspired by his plugin it has a few slight differences, most notably the way in which the off-screen "testing" takes place. In his plugin (apparently inspired by Facebook’s implementation) a DIV is created off-screen and is filled with the textarea’s value whenever it changes. The height of this DIV is retrieved and then applied to the textarea. My plugin makes use of the scrollTop DOM property to gain the true height of the text and then applies that directly (or via animation) to the textarea.

7 jQuery Plugins to Manipulate TEXTAREAs | Steve Reynolds Blog

jQuery Auto Save form elements

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Plugin for auto submitting (saving) a form onchange.

Textarea Behavior Something that I never realized before is that text areas are drop targets by default. Using this property alone (without registering drag events on the source elements), we can emulate drag and drop behavior of non-linked images between different documents. If you drag any of the images on the right side to the textarea you will see the url of the image in it. This works in all browsers except, as anyone could expect, in IE, which doesn't allow you to drag images to input fields.

textarea { overflow: auto; }