Just now Hasin Hayder, author of multiple books, has published a blog post how to host any wordpress.com blog virtually anywhere you wish. Using this simple script, you can host any wordpress.com blog in your own domain.
He wrote a simple proxy script and some codes in .htaccess file. Then the proxy script will fetch all contents from your original blog and show in your site.
Suppose, you have a blog in WordPress.com which URL is www.rajuru.wordpress.com. Using this script, you can host this same blog to somewhere like www.yourdomain.com.
The script does not yet support commenting. Currently it will redirect you to original blog for comment. But the author has just confirmed me that he will implement this part very soon.
For details, visit Hasin Hayder’s Blog