The big three have got there heads together on another nofollow style project involving canonicalisation. They've come up with a header tag which lets you identify which version of a page is the original and therefore avoid any duplication issues. The new tag i supposed to reallocate all the link juice to the chosen page as well!

Here's some more info from big g - http://googlewebmastercentral.blogspot.com/2009/02/specify-your-canonical.html

Note the above post uses of rhetoric such as "It's a hint that we honor strongly" so this may not be a fool proof method to sort out duplicate content and Ill stick to using the good old htaccess and robots.txt to avoid duplicate issues!

There's a bit more of an independent analysis here: http://searchengineland.com/canonical-tag-16537

Joost de Valk has already done a wordpress plugin as well: http://yoast.com/canonical-url-links/