There's stuff even an old fart like me doesn't have the last word on. :D
Check out Canadian Musician http://www.canadianmusician.com/
for all kinds of info on the business side of making music. Even if you're not in Canada, The Biz is pretty much the same everywhere.
This mag covers every side of playing music, on any instrument. Its refreshing to find out just how much we string-slingers have in common with woodwind or keyboard players.