<!-- This requires no customization, but will load a new copy of the bookmarklet every time it is clicked. -->
<a href="javascript:(function(d,t){var timestamp=new Date(); var g=d.createElement(t),s=d.getElementsByTagName(t)[0]; g.src='http://dev.local.com/scripts/mybookmarklet.js?v=' + timestamp.getTime(); s.parentNode.insertBefore(g,s)}(document,'script'));">My Bookmarklet</a>

<!-- This implements a check to see if the bookmarklet has already been called, and if so, it simply re-runs the init function. You'll need to customize MyBookmarklet to the name of your object -->
<a href="javascript:if(!window.MyBookmarklet){(function(d,t){var timestamp=new Date(); var g=d.createElement(t),s=d.getElementsByTagName(t)[0]; g.src='http://dev.local.com/scripts/mybookmarklet.js?v=' + timestamp.getTime(); s.parentNode.insertBefore(g,s)}(document,'script'));}else{MyBookmarklet.init();}">My Bookmarklet</a>