Just add this little code snippet
<a href="http://www.bookmarkingtool.com/index.php?url={$URL|escape|trim}&title={$TITLE|escape|trim}"><img border="0" alt="Social Bookmarking" src="http://www.URLTOYOURIMAGE.com" width="252" height="24"></a>what exactly is the service that bookmarkingtool.com provides?