tomi33

Allows custom “link” post type which adds a Link URL value custom meta box to the post editor
This allows the posts to be easily redirected to the value of that link. (This will involve a small amount of code in the template used to display posts)
The main idea behind this is that you can easily build up a collection of links which you can tag with various key words.
From this you can quickly set up something in your templates/theme of choice to display related links on your blog posts or other pages along with a thumbnail without the need to type in the same links on all the pages
Note: This plugin does not do the redirect for you, you will have to do that within your chosen template
<h3>Instructions</h3>
Click “Links” just below “Posts” in the right hand side admin panel and create a new post, then give it a title, featured image and a link url value.
In your preferred method of displaying a list of links on the site, simply pull in the 3 attributes mentioned above to easily construct a link which you can customise with an image or different title, or change entirely.

Link Post Type

Allows custom "link" post type which adds a Link URL value custom meta box to the post editor

dangrossman

The Calais Archive Tagger plugin automatically goes through your archives and tags every post you’ve written. The plugin uses the Open Calais API to perform semantic analysis of your post text and suggest tags. If a post already contains a suggested tag, that tag isn’t added, but other new tags found are. It takes about 5 minutes to tag 200 posts.
This plugin requires PHP 5 and the cURL library (both of which are available on most web hosts).
Also see <a href="https://wordpress.org/extend/plugins/calais-auto-tagger/" rel="ugc">WP Calais Auto Tagger</a> for suggesting tags as you write new posts.

WP Calais Archive Tagger

Goes through your archives and adds tags to your posts based on semantic analysis.

Link Post Type vs WP Calais Archive Tagger