For Science I use the library or the internet.  I just came across a cool site today that I might use when we finish our human body lesson.

 Another one I plan to use Insha Allah next year is about Astronomy.  

I am trying out the Well trained mind method.  Where you focus on 1 or 2 areas of Science per grade.  For example 2nd grade will be Earth Science and Astronomy.  Then it will be taught again I believe in 6th grade and maybe 10th Insha Allah.