A Worpress Plugin
The internal link building plugin is the Wordpress plugin that helps you easily interlink your blog posts, tags and articles.
All you need to is to (1) choose keywords (you can set the match type as well as set the words to be case sensitive) and (2) give the URL to link that keyword / key phrase to.
You can make links nofollow (It may be useful if that link is an external affiliate link).
You can mass-upload keywords. If you link that keyword to anything else when creating or editing an article, this will override plugin settings.
Use internal link building plugin to bring your older articles back to life as well as help your readers to easily find more information from your archives. Use this plugin to improve your rankings too by creating more in-context links to your deep pages.
The plugin should not be over-used to prevent your articles from looking spammy.