zubairphp

or plz see this

http://ww.wp.xz.cn/extend/plugins/post-plugin-library/

from here you can download that plugins after that install it in you blog site,

or

create .php file using following code and save it with name
similar-posts.php

======================================

<?php
/*
Plugin Name:Similar Posts
Plugin URI: http://rmarsh.com/plugins/similar-posts/
Description: Displays a highly configurable list of related posts. Similarity can be based on any combination of word usage in the content, title, or tags. Don’t be disturbed if it takes a few moments to complete the installation — the plugin is indexing your posts. Instructions and help online. Requires the latest version of the Post-Plugin Library to be installed.
Version: 2.6.2.0
Author: Rob Marsh, SJ
Author URI: http://rmarsh.com/
*/

/*
Copyright 2008 Rob Marsh, SJ (http://rmarsh.com)

[huge chunk of code moderated – please use a pastebin]
=================================

Hello,

plz give me your mail id my mail id is

[email protected]

then I give u full information about you can call smiler post of related post in your site at particular places.