Vladimir Prelovac

WP Digg This is a plugin that adds a Digg button, but with a twist. Instead of adding a Digg button to all your posts, WP Digg This plugin selectively adds the button only to posts you want.
To add a digg button just add a ‘digg’ custom field with value ‘1’.
WP Digg This can display digg button on your single pages but there is an option to show them on home and archive pages as well.
Plugin by <a href="http://www.prelovac.com/vladimir" rel="nofollow ugc">Vladimir Prelovac</a>.
<h3>License</h3>
This file is part of WP Digg This.
Category Search is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
Category Search is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with Category Search. If not, see <a href="http://www.gnu.org/licenses/" rel="nofollow ugc">http://www.gnu.org/licenses/</a>.

WP Digg This

Provides an easy way to selectively add Digg button to your posts. Use 'digg' = '1' custom field in the post to promote it.

goldenapples

This plugin aims to support community link-sharing, social bookmarking, and discussion of links in the WordPress environment.
This is still at an early stage of what I hope will be a much more ambitious project. If you want to try this out, please give me feedback.
I will guarantee backwards compatibility with all data saved by the plugin, so it should be safe to install and activate, and as I add features, your existing posts and links will work with them just fine.
See the plugin’s <a href="https://github.com/goldenapples/recommended-links/wiki" rel="nofollow ugc">wiki page on github</a> for more up-to-date documentation (its hard to keep documentation updated in multiple places).

WP Digg This vs Recommended Links for WordPress