SUMMARY: Completely unrelated to dogs, but I think that the "Nuval" (Overall Nutritional Value Index) is the best nutritional aid to come along in a long time.
Nuval rates every food on a scale from 1 to 100 for its nutritional value. Developed at Yale, it's based on a variety of nutrients, grains, vitamins, sugar, salt, impact on blood pressure, and a bunch of other things. I first read about it in a brief article in the Sept 2008 National Geographic.
Think how handy it would be to compare an orange at 100 or a tangerines at 93 with canned sweetened mandarin oranges (haven't found a score for them yet, but I'm betting it's quite a bit lower). Or to compare your Wheatena at 91 with Wheaties at 28. Or Captain Crunch at 10. (Not that I'm admitting to eating it regularly.)
Sure, some of this you could kind of guess on your own. But this really makes it easy to compare. They're trying to get grocery stores everywhere to use it. I would love to see this implemented.
You can read scores for quite a few things already at nuval.com.