This is just a port of the hack made by Gary_King for 3.0. Original thread here.
The code was actually written by Andreas. I merely put it all together in a plugin for the users that requested it.
This is an updated version of my original release.

Install instructions:

1. Import the plugin
2. Edit the postbit or postbit_legacy template (or both).
find:

PHP- Kodu:
<div>$post[icqicon] $post[aimicon] $post[msnicon] $post[yahooicon]</div> 
above that, add:

PHP- Kodu:
<if condition="$groupstr != ''"><div>
$vbphrase[member_groups]: <br>$groupstr
</div></if> 
3. Add a new phrase called member_groups containing:

Kod:
Member of