he's just using the built in vbulletin dhtml menus
Here's the two key pieces of code to achieve this.
Above is the code for making the link in the posbit. I left the original code in there for an example
Tag: <a href="http://xboxlive.teamxbox.com" title="Click to view Shockwave's GamerCard"><b>Shockwave</b></a>
Above is the physical popup that you get when you click on the shockwave link.
<div id="gamercard_$post[postid]_menu" style="display:none">
Put your popup data in here
Once you have the link integrated into your postbit, you can paste the second bit of code either at the very top or bottom of the postbit and enter your goodies that you want displayed. Try not to embed it in any other HMTL tags because the style="disaply:none" can cause issues.