Grist did a taste test among a bunch of different fairly traded organic cocoa mixes.
It’s a sort of amusing read–and I love how in the end she comes to the same conclusion I did a couple of summers ago (summer? cocoa? Who drinks cocoa in the summertime? er…I do.)–which is that if you buy your own decent unsweetend baking cocoa, you can make your own homemade cocoa in only a few seconds more than it takes to do the mix stuff, for a fraction of the cost and ultimately better flavor.
Skip the mixes. Not worth it. Make your own.