One way to save money is to cut out the middle man. This concept can be applied to our curriculum purchases. Some publishers will give discounts, as deep as 50%, if individuals place a bulk order. If you contact your fellow homeschoolers, you may just be able to get enough orders for such deep discounts.
We have someone in our homeschool support group who use to take orders once a year for a favorite publisher and as a result we enjoyed a 40% discount.
Now every publisher has different rules, so you need to take the initiative to contact your favorite publisher and ask. Some publishers require that purchase 10 of the same title, while another may only require that you buy $200 worth of any books. Larger publishing houses may require that you be an established business with a tax ID number.
Also, if you have a favorite education or children's magazine you may be able to get a discount for your homeschool group. In the case of magazine subscriptions, you will need to find out if the bulk order has to go to a single address, or if you can have the magazines sent to individuals.