In our school we use the SWH (Science Writing Heuristic) approach to science. I absolutely LOVE this!
Our big idea for this unit is: Objects in the sky move in different ways.
Last year we learned about a lot of different things in our sky.
We talked about day and night and rotation and revolving and SPACE. These kids wanted to know EVERYTHING about space they could! To show what they learned they got to choose a "final project". They could make a poster, a model, a computer project, a mobile. etc. They had to come up with a plan and tell me the materials they needed and how they would complete their project. A lot of the kiddos chose posters and models, 1 student made a power point slide show, and 1 made a mobile. They then presented them to the kids in Kindergarten in a "mini" science fair.
This year we are making a space fact book. Each year we try to do something different. :)