qualified_free_shipping.rb

class Spree::Calculator::Shipping::QualifiedFreeShipping < Spree::Calculator
    preference :minpurchase, :decimal, :default => 0
    attr_accessible :preferred_minpurchase

    def self.description
        Spree.t(:qualified_free_shipping)
    end

    def compute(package)
        return 0
    end

    def available?(package)

        item_total = 0

        package.contents.each do | item |
            item_total += (item.variant.price * item.quantity)
        end
        (item_total >= BigDecimal(self.preferred_minpurchase.to_s)) ? true : false
    end
end

Load in config/initializers/spree.rb with the following:

Rails.application.config.spree.calculators.shipping_methods << Spree::Calculator::Shipping::QualifiedFreeShipping

Try this in 1.3
in config/application.rb

        config.spree.calculators.shipping_methods << Spree::Calculator::Shipping::QualifiedFreeShipping

@rterbush have you made any more adjustments on this calculator for Spree 2.0.3 update? It seems to be throwing an error now when I continue past /checkout/address: undefined methodeach' for #Spree::Stock::Package:0x007fb7e0c43c50` at line 17 of this file