Druids may use any ranged weapon that is not refined or that does not use objects that may harm the connection with nature. Such objects may include pulleys, or metal. Acceptable ranged weapons at this time are slings, shortbows, or longbows.
Really though, I think you'll find you won't use distance weapons terribly often after early levels, since electrocuting, burning, or freezing your enemies is much more fun.
Metal is natural, too, even
that has always been my belief, and why I always found it odd, for some of them to shun metal to the highest point.