http://www.christianbook.com/ is having a 35% off sale on Apologia resources. This includes their science books and their supplemental books like Around the World in 180 Days (World History and Geography).
Write down this code for free shipping thru 9/10 (on orders over $35): 313114TS. I just used it today and it worked.
The sale on Apologia is only good through the end of this month (August).