I love these little projects and will be doing some of them for my pre-k son. They are unit studies and focus on all of the subjects. I believe it is from "Five in a Row" which incorporates a number of activities in different subjects based on reading one book per week.
http://www.homeschoolshare.com/Level2.php
We still aren't sure about the curriculum for my 7 & 9 year old. I'm waiting to hear what the school district is offering. But I'm really excited about "The Story of the World" so I will probably go that route and they will both study the same time period.