It goes without saying that you should NOT nofollow every single outgoing link on your website. It not only makes search engines such as Google suspicious, the practice is not really that wise. There is nothing wrong with linking to other top sites in your niche market but you do want to nofollow links to sites that you are not too familiar with. You can always do this manually. The Ultimate Nofollow saves you time by adding a check-box to WordPress’ Insert/Edit link popup box.
The idea here is simple: most of us rely heavily on the Insert/Edit link popup box to add internal and external links. When you install this plugin, you will be able to nofollow links before adding them to your posts. The plugin also has options to nofollow links in other parts of your website (e.g. your blogroll links) but that’s not the reason I am using it.
Ultimate Nofollow is pretty simple and makes it easier to add the nofollow attribute to your links before including them in your posts. You can do this manually but why waste time that way?