Hi,
Adding a Digg Button to all blog posts in blogger is really simple and interesting. You only need to change a code in your HTML with the code mentioned below.
Look for the following code in your HTML
<p><data:post.body/></p>
And replace it with
<div style='float:right; margin-left:10px;'> <script type='text/javascript'> digg_url="<data:post.url/>"; </script> <script src='http://digg.com/tools/diggthis.js' type='text/javascript'/> </div> <p><data:post.body/></p>
You are done. All of your Blog posts will have a Digg Button now.
For detailed instructions with pictures visit here