Related posts pro provides a nice and powerful solution for all kinds of related content. Handles custom post types, multisites, categories, terms, mixed content, custom content and many more…
The plugin comes with three beautiful layouts
It’s not always about the visitor. A high quality, confortable backend can save you a lot of time – this is also provided by Related Posts Pro. More than 200 optimally pre-defined options will give you the highest possible customisability level without touching the code. Why don’t you try it?
The plugin comes with a very descriptive documentation in both PDF and HTML formats. You can read them both before buying.

Future release plans: - Relevance by views, likes and current content tags - Plugin exclusion from page ids - Image crop position definition Changelog: 2014.07.01 - v1.0 - Initial Release - Look in posts, pages, custom post types - Look in title, content, excerpt, custom fields - Smart image creation with TimThumb or built in image parser - Custom content creator - Shortcode available for posts and themes - Auto placement below/above content - Excluding posts,pages - Excluding categories - Excluding words in a stop-file - 150+ theme options, 65 pre-defined themes: neo, metro, minimal, artsy, magazine, pinteresting - 3 layouts: Isotopic (based on jQuery isotope), Slick and Slide and Transitioning (based on Codrops transitions) - Compatibility levels - Built in caching options - Hooks available