Probably the best widely available chocolate would be Guittard. Guittard is run by Gary Guittard and it was started by his great grandfather in San Francisco during the gold rush. I'm personally good friends with Gary and I know where they buy their beans (not all of them but enough so that I have a good sense as to what is paid and we buy from some of the same farmers.) Guittard buys some very premium cocoas (and some lower grade too.) For their premium cocoas, they pay premium prices. Gary (along with myself) are founding members of Direct Cacao an organization that was set up to promote the direct trade of cocoa with the farmers to help ensure that farmers get paid enough to keep cocoa a viable crop and to help keep quality up.
Lindt actually owns Ghiraldelli which is funny. When you buy San Francisco Chocolate, you are actually buying swiss. I'm familiar where they get some of their beans and their beans generally aren't particularly good quality. Their Madagascar chocolate is made with some of the lowest quality cocoas from Madagascar for example -- they couldn't buy their cocoa from the better growers for example Akkeson's plantation where we, Valrhona, and many of the europoean manufacturers buy their cocoa from.
Chocolate brands to look out for would be IMHO: Michel Cluizel, Pralus, Amedei, Domori, Valrhona (though they don't us as good cocoa as they used to). In the US, I'd look at companies such as Guittard (the big one) and smaller ones such as Amano, Theo, Patric, Rogue, Dandelion, Askinosie, Taza, Ritual, Dick Taylor, Fresco, Patomic, etc. There is a new movement in the US for craft chocolate making much in the same way the beer industry went a few years ago. These companies (and others) are at the forefront and many of their owners truly care about what they are doing and the farmers they work with. Among many of these companies is the desire to be part of the solution rather than part of the problem. I've been immensely proud to hear how the owners all want to pay the farmers more. Gary Guittard in one of our Direct Cacao meetings got up and specifically said: "We all need to pay even more to the farmers." I was so proud to be part of a movement where this was being said. The biggest hurdle is to educate the public so that chocolate isn't seen as just another commodity so that the public is willing to pay enough that we can pass that along to the farmers as we would like.