This is the Vikinghammer Tweet plugin.
You can set it up to post tweets based on new posts or comments to your blog. This requires that you enter your Twitter credentials.

Vikinghammer Tweet

Send a tweet for any new post or comment to your blog.

metaphorcreations

Custom pack of widgets including shortcode generators.
<ul>
<li>Twitter</li>
<li>Social</li>
<li>Recent Comments</li>
<li>Recent Posts</li>
<li>Tabbed Posts</li>
<li>Contact</li>
<li>Post Navigation</li>
<li>Collapse</li>
</ul>
<h3>Advanced Info</h3>
Each widget includes a shortcode generator. Copy and paste the shortcodes into your posts to display the widget contents anywhere on your site.
Each widget also displays the widget ID of the widget. This can be helpful if you wish to use any of the filters built into the widgets.

Metaphor Widgets

Custom pack of widgets including shortcode generators.

Vikinghammer Tweet vs Metaphor Widgets