mikegogulski

Pingcrawl aims to replicate WordPress.com’s “Possibly related posts” capability. It queries Google Blog Search for related blog posts (based on tags, or the post title if there are no tags), tries to verify that they are pingback/trackback compatible sites and, if so, adds links to such posts to the end of each blog post where it is invoked.
Scope-limiting configuration options are included to enable Pingcrawl to fit any WordPress installation’s memory/execution time budget.
<h3>Licence</h3>
Pingcrawl is free software released under the GPL. If you find it valuable, you’re invited to make a <a href="http://www.nostate.com/support-nostatecom/" title="Donate with PayPal, MoneyBookers, etc." rel="nofollow ugc">small donation</a> toward its ongoing support and maintenance.

Pingcrawl

Pingcrawl adds a "Possibly related posts" capability by querying Google Blog Search for post tags and pinging the results.

mihai

This plugin will modify the links on pingbacks (and trackbacks) to remove the 
“external nofollow” for links to your own blog.
More info:
<ul>
<li><a href="http://patchlog.com/follow-self-pings/" rel="nofollow ugc">Follow Self Pings plugin</a>.</li>
<li>Check out the other <a href="http://patchlog.com/wordpress/" rel="nofollow ugc">WordPress plugins</a> by the same author.</li>
</ul>

Pingcrawl vs Follow Self Pings