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.
- Activate the plugin through the ‘Plugins’ menu in WordPress
- When editing your post or page, add a custom field using real_url in the
Namefield and enter the URL of the post you want indexed in
Contributors & Developers
“Duplicate Content Link” is open source software. The following people have contributed to this plugin.