rel="canonical" add it if utm parameters exist in url

Unfortunately Googlebot can sometimes index the utm parameters used to track campaigns in Google Analytics.

For example if my site url is www.example.com/
and I tag my links like so

www.example.com/?utm_campaign=2008_my_campaign&utm_source=google&utm_med...

If someone links to this site with this url often it can get indexed by the search engine which causes duplicate content.

If there is a way to detect these url parameters and output in the section of the document a link tag

You can notify the search engine that this is a duplicate link which will prevent it being indexed. This should also be a standard adopted by Yahoo and MSN

See here for more:
http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=139394