The Roots Music Report is an online resource that reports radio play charts for a number of “roots” genres including bluegrass. Their charts are compiled based on playlists submitted by the stations/DJs. It looks fairly easy to sign up to report your playlist if you are a DJ or station manager, and I would encourage you to do so.
The charts they now have available, like this bluegrass chart, are nation wide reports. The company has announced that in January 2007 they will be launching state specific charts for a number of states including California, Tennessee, Illinois, and New York. The goal is to eventually represent all 50 states with individual radio airplay charts. This should be a great way for artists and labels to see how much their music is being played in specific geographic regions of the country. I would think that comparing the results of the state charts to the national one should be interesting.
It sounds like a lot of work, but it should be quite a resource for the professionals in our industry to track how their music is being distributed on radio.