Duplicate Content Through Sorting

[andertoons]

I have a website that sells images. When you search you're given a page like this:

http://www.andertoons.com/search-cartoons/santa/

I also give users the option to resort results by date, views and rating like this:

http://www.andertoons.com/search-cartoons/santa/byrating/

I've seen in SEOmoz that Google might see these as duplicate content, but it's a feature I think is useful. How should I address this?

[Tompt]

If you use just used robots.txt to block the byrating directory that would probably be simplest. SEOmoz will still flag the pages up as errors but this is an intentional use to reduce duplicate content.

[TellThemEverything]

This is a perfect opportunity to use the canonical tag: http://www.google.com/support/webmasters/bin/answer.py?answer=139394 so that only one of these pages is indexed.