I don’t use related post plugin on my blog anymore, there is no other reason why removed it, I just simply don’t like to use it now.
Recently, I found Yet Another Related Post plugin (http://mitcho.com/code/yarpp) that gives you a list of posts and/or pages related to the current entry, introducing the reader to other relevant content on your site. Some additional features of this plugin are as below:-
1. Limited by threshold
2. Using tags and categories
3. Disallowing certain tags and categories
4. Related posts and pages
5. Simple installation
6. Miscellany
For more information about the installation and related functions to be used, you can check out their site.