Didier Sampaolo

When you write a long post, it is common to add h2 and h3 tags to create sections on a specific topic. This plug-in will search these sections and add a link to each of them at the beginning of your post. Each section will become a named anchor, allowing the user to browse quickly through your post. 
This summary is also understood by major search engines and should improve your CTR (click-through rate) by providing richer snippets.
<a href="http://www.didcode.com/code/wp-summary.html" rel="nofollow ugc">Plugin home page</a>

wp_summary

wp_summary will automagically show a summary of your post at its beginning, using h1, h2 and h3 tags to create sections.

Ben Huson

If you want to spice up your theme layouts this plugin will allow you to show different parts of your content in different area of your theme templates – break out of a single column of content.
More information can be found on the <a href="https://github.com/benhuson/content-parts/wiki" rel="nofollow ugc">Content Parts plugin page</a>.

Content Parts

Divide your post content into parts that you can show in different areas of your theme templates.

wp_summary vs Content Parts