Michael Henke

Insert SEO friendly/neutral links to social networks and bookmarking services. This plugin is proudly provided by <a href="http://www.all-things-seo.com" rel="nofollow ugc">all-things-seo.com</a>.
If you don’t know yet, find out what a <a href="http://www.all-things-seo.com/seo/seo-friendly-social-links/" rel="nofollow ugc">SEO friendly link</a> is. These Links can be inserted automatically above or below each post or manually (e.g. in the theme).
The plugin ships with support for Twitter, Facebook, digg, delicious, buzz, reddit, StumbleUpon, …extend the list by customizing your own services

SEO Friendly Social Links

Insert SEO friendly/neutral links to social networks and bookmarking services.

Nolongeractive

To use the widget just drag it to a sidebar and choose one of six button styles. You can also specify a url to recommend. If you leave the url empty, the active page will be recommended.

Stumble Page Social Widget

This plugin lets you place a StumbleUpon button on your WordPress blog as a widget. You can configure the button by choosing the style and specifying  …

SEO Friendly Social Links vs Stumble Page Social Widget