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).

English 
140follow removes NOFOLLOW from author link if the comment has more than XXX characters. 
The character count can be adjusted at the admin pannel. NOFOLLOW also can be added 
to single comments if you add “/dontfollow” to the end of the author link.
Deutsch 
Das Plugin ersetzt rel=”external nofollow” durch rel=”external” aus dem Autor-Link, 
wenn der Kommentar mehr als XXX Zeichen besitzt. Die Anzahl der Zeichen kann 
einfach im Adminbereich beliebig eingestellt werden.
Einzelnen Kommentaren kann das NOFOLLOW-tag wieder hinzugefügt werden, wenn 
einfach “/dontfollow” (Danke an Oliver Bockelmann) zum Link hinzugefügt wird.

140follow

140follow removes NOFOLLOW from author link if the comment has more than XXX characters.

SMu Manual DoFollow vs 140follow