When ordering curriculum/books by mail order, combine your order with a friend, or a few.
Several homeschooling mail order companies offer free shipping and handling if you place an order over a certain dollar amount - anywhere from $50 to $250. Combining your order with a friend may just give you a large enough order to get free s/h.
Always be aware of shipping costs. I've seen more than one company offer discounts on curricula and then make it up with outrageous s/h.