Regarding shipping KNO3:  All nitrate salts are oxidizing agents.  They 
require special handling via some carriers.  KNO3= saltpeter, an 
ingredient in gunpowder.  Not explosive by itself, but it would certainly 
accelerate a fire.  I would think that this applies primarily to the 
solid, solutions should be safer.  You are not in personal danger when 
handling it, but keep in mind that it is an oxidizing agent.