To create food-style nutritional labels for news would require a common taxonomy for all the world's journalism. But taxonomy is surprisingly political and complicated. Even if you could get major news organizations to agree on a standard (and some already have, i.e., rNews), do you expect millions of independent content producers to follow?
Ethan Zuckerman and his student Matt Stempeck at MIT's Center for Civic Media are undertaking this massive project themselves, using a combination of human and computer labor to categorize many terabytes of news stories. Zuckerman hopes to create an eventual product that would let the user track his or her "news nutrition."
I post this not to be self-promotional but because I think it would be of interest to this community... and I'm curious to hear how you all would attack this problem.
NPR is not trying Google's 20% time, per se; what they call "Serendipity Day" is simply their adaptation of the idea. The next one is planned for September, and the goal is to make it a quarterly event.