For almost every forum software sidebars are available, but not for MyBB. So I created one simple and feature rich plugin. You can find this plugin on Github.
Contains following boxes:
Sidebar variable is only available in the footer template.
To use this Plugin you need the following system:
You can modify and redistribute it under the terms of the GPL Version 3.
Edit template header (e.g. Template Sets → Default Templates → Header Templates → header) and add after:
<table width="100%" cellspacing="0" cellpadding="4" border="0" align="center"> <tr><td valign="top">
Edit template footer and add before:
</td>
{$sidebar}</tr>
</table>