Mosaic - This is a free history curriculum for 1st - 3rd graders.  Currently they have the Ancient World and Medeival World curriculums.  Although it is free, it does use a lot of outside resources as well as several spines that you would need to purchase.  

The Story of the World : This is a 4 part curriculum written in the classical style, but with large appeal over a variety of homeschooling styles.