Stefan M.

This plugin will set all Trackbacks and Pingbacks automatically to DoFollow Links.
The user comments will get after <code>X</code> comments from a unique mailaddress automatically DoFollow status. All other comments have NoFollow, except the Admin enable manually the DoFollow Status. The status which is set manual (if DoFollow or NoFollow) will overrides the automatical process. So, you have the control if someone gets sooner the DoFollow status, or never maybe. Of corse, the automatism can be disabled to do the hole work manually.
You get an support automatism, that you don’t need to check daily, but have the full control power.
Additonal this plugin validated all DoFollow URLs and will notice if there are broken links. Broken Links are very bad the Rank in the Search Engines (SEO).
Home Page of the Plugin: <a href="http://blog.murawski.ch/2010/09/wordpress-manual-dofollow-plugin/" title="IT Blögg - WordPress Manual DoFollow Plugin" rel="nofollow ugc">IT Blögg – WordPress Manual DoFollow Plugin</a>
If you have a wish for new functions, please contact me.

SMu Manual DoFollow

SMu DoFollow has many DoFollow Options (Manual or Automatism) and included URL Validator (Manual, WP-Cron or Cronjob).

Everfluxx

Follow My Links is a very simple plugin that prevents WordPress from automatically adding a “rel=nofollow” attribute to the following two categories of authorial links: 
1. links in the post author‘s comments; 
2. links to the post author‘s URL (usually linked to from the comment author’s username).
<a href="http://www.everfluxx.com/follow-my-links/" rel="nofollow ugc">Read the full documentation at Everfluxx.com!</a>
<h3>Donations</h3>
If you like this plugin, feel free to donate a link to <a href="http://www.everfluxx.com/" title="www.everfluxx.com" rel="nofollow ugc">my blog</a> or <a href="http://tinyurl.com/followmylinks" title="Donate with PayPal" rel="nofollow ugc">buy me a slice of pizza</a>.
<h3>Feedback</h3>
Please do send me your feedback via this <a href="http://www.everfluxx.com/follow-my-links/#respond" rel="nofollow ugc">comment form</a>.

Follow My Links

Do not automatically add the rel=nofollow attribute to links in authorial comments, strip nofollow from links to the post author's web page.

SMu Manual DoFollow vs Follow My Links