Konrád Koller

Do you like to write long articles with many headers? Then this is the perfect plugin for you. This plugin will add a link next to your headers so your user can share your posts pointing to specific parts. Plus a smooth scroll script is also included which will make the overall experience even better.
The package contains a predefined style for Git-like link display but it is hardly recommend to change the style to fit your needs (and your design).
The plugin uses internal cache which may interfere with other cache plugins, if you experience anything strange feel free to contact the plugin author.

ONet Header Linkifier

For advanced users! Github-like header parser for your posts, pages and custom contents. Also lets you fetch TOC for any content.

KilukruMedia

Simply add anchors links inside your content. Shortcode <code>[wpanchor id="your_id"]</code> is added via a button in Wisiwig. After your need to create a link inside your site with #your_id for the href link. Your link look likes <code><a href="#your_id">my link</a></code>

WP Simple Anchors Links

Insert simply many anchors to pages, posts and custom post type.

ONet Header Linkifier vs WP Simple Anchors Links