Every time you modify a post slug, add a new post, rename a category, or otherwise modify any of your post and page permalinks, jadedcoder Sticky Permalinks (jcsp) will keep a copy of the original permalink along with the post or page it originally led to. If anyone tries to access the old URL, they will be redirected right to the new one, no matter how many times you’ve changed it.
If you re-use a URL that has already been used in the past, its copy will be replaced and it will safely link to the new article instead.
Don’t throw away valuable URLs! This plugin lets you re-organize your site as many times as you want, without risking traffic loss.

jadedcoder Sticky Permalinks

Keeps a history of your permalinks no matter what changes you make on your site, and redirects old links to the new ones.

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.

jadedcoder Sticky Permalinks vs Vote It!