tinyMCE

HTML

<script src="http://tinymce.moxiecode.com//js/tinymce/jscripts/tiny_mce/tiny_mce.js"></script>
<script src="http://tinymce.moxiecode.com/js/tinymce/jscripts/tiny_mce/classes/adapter/jquery/jquery.tinymce.js"></script>
<script src="http://code.jquery.com/ui/1.8.23/jquery-ui.min.js"></script>
<link rel="stylesheet" href="http://code.jquery.com/ui/1.8.23/themes/redmond/jquery-ui.css">
<div id="myTab">
    <ul>
        <li><a href="#tabs-1">Tab 1</a></li>
        <li><a href="#tabs-2">Tab 2</a></li>
    </ul>
    <div id="tabs-1">Tab 1 content</div>
    <div id="tabs-2">
        <textarea class="tinyMCE">Textarea content</textarea>
    </div>
</div>

JavaScript

tinyMCE.init({
    mode: "specific_textareas",
    editor_selector: "tinyMCE",
    theme: "advanced"
});

$("#myTab").tabs();