My school teaches the Core Knowledge Sequence (I love it!) and in first grade one of the things we teach is Ancient Civilizations. We cover Mesopotamia, Egypt, Hunters & Gathers, the Aztecs, Mayans, and Incas. The kids have been sucking it right up. It has really been a blast to learn about. Honestly, I'm a little embarrassed to admit that before teaching about it I didn't really even know what Mesopotamia referred to!
We started by learning about what history is. One of my team teachers provided this awesome packet she purchased over the summer with excellent activities for each of the civilizations, and I've created a few of my own to supplement.
Then we studied Mesopotamia. The kids loved writing in Cuneiform on clay tablets (i.e. playdough :) and we finished the unit by building a ziggurat out of sugar cubes!
We recently finished Egypt (pictures to come) and now we're finishing up the Aztecs & Incas and compiling everything in the book pictured above with pockets for storage.