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.

surdotly

Sur.ly alters the outbound links on your site so that visitors can view external target pages without leaving your domain.
Feel free to check <a href="http://wordpress.demo.sur.ly/?p=1" rel="nofollow ugc">Sur.ly demo tour</a>.
Sur.ly plugin replaces the outgoing links in comments, posts, etc (except for whitelisted links of your choice) with the links leading to intermediate pages on your subdomain. When users follow these links, they will seamlessly view the external target pages while technically staying within your domain.
<a href="http://sur.ly" rel="nofollow ugc">Sur.ly</a> accompanies, informs and protects users when they follow outbound links, so they can never bump into an adult or malware-infected content under links posted by other visitors.
<a href="http://sur.ly" rel="nofollow ugc">Sur.ly</a> can help you to:
<ul>
<li>Get rid of toxic and unsolicited outbound links.</li>
<li>Turn any risky outbound links into safe internal links to avoid Google penalty.</li>
<li>Cope with fake users signing up for your site to get backlinks.</li>
<li>Recapture users leaving via outbound links.</li>
<li>Keep users within your domain longer to reduce the bounce rate.</li>
<li>Shorten links down to neat and convenient alphanumeric identifiers.</li>
</ul>

Sur.ly

Sur.ly alters the outbound links on your site so that visitors can view external target pages without leaving your domain.

Vikinghammer Tweet vs Sur.ly