SO fiddle

Test Fiddle mainly for SO Questions

by Nick Craver

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
<textarea id="post_body"></textarea>

<blockquote><span></span></blockquote>

CSS

blockquote span { white-space: pre; }

JavaScript

$('#post_body').keyup(function() {    
    $('blockquote').find('span').text($(this).val());
});