I know there are a lot of widgets and plugins for WordPress out there for adding a Digg badge to posts (I know, because I tried half a dozen or so of them) but I didn't find any that worked consistently and provided the functionality I wanted. After researching the Digg Tools API and a few other examples online, I've composed this block of code for generating Digg badges.

To add a Digg badge to your WordPress posts or pages, simply add the following code block immediately before or after the PHP block that contains the_content(). For posts, you would want to modify the Main Index Template, Single Post, and Archives theme files. For pages, you simply need to modify the Page Template theme file. Here's the code:

<div class="diggLink">
    <script type="text/javascript">
        digg_url = '<?php the_permalink() ?>';
        digg_title = '<?php the_title(); ?>';
        //digg_topic = 'TOPIC'; // replace TOPIC

        /*
        Use the output buffer to capture the text
        output from the_ID() rather than having
        it rendered to the page.
        */

        digg_bodytext = '<?php
            ob_start();
            the_ID();
            $postID = ob_get_contents();
            ob_end_clean();

            /*
            Get the body of the post, remove HTML,
            remove carriage returns and line feeds,
            escape 's, return only the first 350 char.
            */
            $postObj = get_post($postID, OBJECT);
            $body = strip_tags($postObj->post_content);
            $body = str_replace(chr(10), '', $body);
            $body = str_replace(chr(13), '', $body);
            $body = addslashes($body);
            echo substr($body, 0, 350);
        ?>';
    </script>
    <script src="http://digg.com/tools/diggthis.js"
        type="text/javascript"></script>
</div>

I've also added a class to the wrapping DIV and added it to the stylesheet for my theme to style the positioning of the Digg badge. I place the above code right before the the_content() block and this CSS class is what positions my Digg badge to the right of my posts.

.diggLink
{
    float: right;
    margin-bottom: 4px;
    margin-left: 4px;
}

If you'd like to set your posts to all submit to one particular topic, you can uncomment the line that refers to digg_topic in the code block and then change TOPIC to the topic you'd like to use. You can find the list of topics on the Digg Tools API page.

If you have any questions, feel free to comment and ask me. By the way, this same code block is currently in use at Pac Ten Review.