LoudSkyMedia

This simple plugin permanently redirects all 404’s to the main blog URL. There may be several reasons why you might want to do this, but the primary purpose is to siphon Google Page Rank (TM) from missing pages to the homepage.

404 Redirection

Permanently redirect all 404's to the main blog URL. The primary purpose is to salvage Google PageRank (TM) from missing pages.

tzangms

This plugin is originally written for blow.media, it will find the right post from various URL pattern. Especially permalink starts with <code>/%post_id%-%postname%/</code> format.
Allows patterns below
<ol>
<li>/%post_id%-any characters/</li>
<li>/%post_id%/</li>
<li>/%postname%/</li>
</ol>
This plugin searches for post_id and post slug in url, if the post is found, this plugin will redirect visitor to the latest permalink of post, so you can change your permalink structure as you wish without worrying about the missing link problem.

Blow Link

Find the right post from various URL pattern. Especially permalink starts with post_id.

404 Redirection vs Blow Link