At the top of each page on urlBorg you will se a link named "account". Click on it and login using your GMail account.
You will be redirected to your urlBorg account page, where you will se the option "enable previews". Previews are simple pages that look like this (here, I take advantage of a hidden urlBorg feature: if you add /p at the end of a short URL you "force" the preview to show up). Their obvious value is to protect you from going to pages you wouldn't like to visit, but their URL is hidden by urlBorg.
I think "previews" can be much more. Here are a couple of features I already implemented.
MP3 files If a URL goes to an MP3 file (determined by the MIME type reported by the hosting server), the preview will also show you flash mp3 player that allow you to listen to it. Here is an example.
maps For this one, I have to thank Raphael from U.[lik]. Raphael is has been using urlBorg to share links to Google Maps (those links can be long and ugly). Now, if you link to a page in Google Maps or Yahoo! Maps, the preview will also display a link to the other service, where you will se the same map.
Here is a Google Maps expample (again, note the /p at the end of the URL) and a Yahoo! Maps example. You don't have to do something special. urlBorg will examine the structure of the link and display automagicaly the "extra info".
So, what do you think?