I just wrote a skeptical piece about the search engines’ new rel=canonical standard.
I am, after all, a skeptic.
But, if you’re a large publication with a massive site, you’ve got canonicalization problems, and this could be the solution you’ve been looking for.
In a nutshell: You can use rel=canonical in the HEAD element of pages you don’t want indexed, and search engines will list the URL you indicate, instead.
No guarantees on whether this will actually help with search engine optimization, but given how difficult it is to clean up these kinds of problems on larger sites, it’s worth trying rel=canonical for a few months.
Read more about the standard on the Google Webmaster Central Blog.