I just down­loaded this awe­some iTunes plu­g­in called iCon­cert­Cal. It uses the iTunes index and then search­es for artists in your playlist and makes a cal­en­dar show­ing when and where they’ll be in your area. It isn’t fool­proof, since I imag­ine small­er groups aren’t going to be eas­i­ly found, but it is cer­tain­ly bet­ter than check­ing every venue’s site reg­u­lar­ly.