The rel canonical HTML element is one of my favorite tools to use in SEO. Google tends to understand the code well, it can help transfer page rank accurately and it is usually very easy to implement.
In this video, Matt Cutt’s, head of Webspam at Google, discusses the rel canonical tag and how it can be used by publishers to deal with small duplicate content issues. While that is the case, the rel canonical attribute can be used in more ways than one.