I am after no follow links for link diversity. Can you recommend a good way of obtaining these from authority sites?
You can get some pretty sweet authority links from Amazon (as a reviewer) and from Facebook in your profile. Tried Google+ yet? Last time I checked I believe they were nofollow. Those are pretty big authority sites
But you can also use add-ons on firefox in checking no follow and do follow tags. and yes mos of authority especially TLD's are no follow even social networking sites are no follow.
i would not spend any time specifically to build nofollow links. just keep building links and some of them will end up being nofollow anyways.