Thamizhchelvan

Asad Zulfahri

Nofollow Links in Posts plugin enables you to add the “nofollow” attribute into links in a post within a specified category. This plugin 
is useful if you are doing sponsored posts. You can set the plugin to add the “nofollow” attribute for posts older than “X” days.

Nofollow Links in Posts

Adds the rel="nofollow" to links in posts within a selected category. Useful for sponsored posts.

patrickcurl

The NoLiP plugin enables you to add the “nofollow” attribute into links in a post within a specified category. This plugin is useful if you are doing sponsored posts. You can set the plugin to add the “nofollow” attribute for posts older than “X” days.
Originally the Nofollow Links in Post Plugin found here: 
http://www.themiak.com/wp-plugins/nofollow-links-in-posts/

Nofollow Links in Posts vs NoLiP – Nofollow Links in Posts Reborn