I have a chunk of javascript that users can copy and paste to put on their sites.
I'm currently using the following code (ala WEDJE) that allows the rest of the page to load even if my script is slow or not responding.
<script type="text/javascript">
var number = "987654321";
var key = "123abc";
(function(){
document.write('<div id="ttp"></div>');
s=document.createElement('script');
s.type="text/javascript";
s.src="http://example.com/javascripts/embed.js?" + Math.random();
setTimeout("document.getElementById('ttp').appendChild(s);",1);
})()
</script>
But that method is a few years old and so I wasn't sure if there was a more efficient way of doing the same thing that others have come up with.