WordPress plugin Update
MQ ReLinks is a wordpress plugin which allows you to easy redirect all external links in posts, pages, comments, author and widget links, without passing link juice.
In stead of a direct link to another site, the plugin will create a link to a out.php file that will redirect to the requested URL. They can be opened in a new window or in the same one.
You can configure the post, comment and author link options in the administration area.
Go to plugin page