Yesterday, WordPress Optimization Guide hit the front page of Digg and I needed a plugin to selectively show Digg button so I mashed up a new plugin  to handle the occasion. I called it WP Digg This, and it allows you to select articles you want to show Digg button on, simply by adding a custom field to the post with key 'digg' and value '1'. Very simple and it works. This is much better then showing Digg button on all pages of your site.