DZVO

This plugin allows you to display a buttons which shows the voting for a social news message (digg,sphinn …) on your blog post. 
You will find a collection of voting buttons for different social-news-services <a href="http://www.zauberpage.de/vote-it-liste.html" rel="nofollow ugc">here</a>.

Vote It!

Vote It! Buttons for Blogpostings. Set very simple a digg, sphinn or another social-news-button in your blogpost.

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).

Vote It! vs Recommended Links for WordPress