Duplicate Content Link

Google released a new way to notify them of duplicate content so that it is not indexed and penalized. http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html

This plugin allows for you to link to another post or your home page from each post or page that is written letting Google know it is duplicate content.

This is a stable version.

1. Upload duplicate to the /wp-content/plugins/ directory
2. Activate the plugin through the ‘Plugins’ menu in WordPress
3. When editing your post or page, add a custom field using real_url in the Name field and enter the URL of the post you want indexed in Value field.