jQuery Version

JavaScript (modified from a script I found on someone's site - I just can't find the site again, so I can't give the person credit):

$(document).ready(function() {

  $("#bookmarkme").click(function() {

    if (window.sidebar) { // Mozilla Firefox Bookmark

      window.sidebar.addPanel(location.href,document.title,"");

    } else if(window.external) { // IE Favorite

      window.external.AddFavorite(location.href,document.title); }

    else if(window.opera && window.print) { // Opera Hotlist

      this.title=document.title;

      return true;

    }

  });

});

HTML:

<a id="bookmarkme" href="#" rel="sidebar" title="bookmark this page">Bookmark This Page</a>

IE will show an error if you don't run it off a server (it doesn't allow JavaScript bookmarks via JavaScript when viewing it as a file://...).