The girls and I have long since loved the Dupage Children's Museum in Naperville. We have been to more than a dozen such museums and DCM is the Cadillac of them all, in my opinion. I could play there all day~without the kids. The first floor is divided into section relating to Light, Sound, Construction, Air and Water.
In the Light area, you can play with shadows, light pens, color, mirrors, and hmmm...what shall I call it? An enormous Light Brite under blacklight. It is the coolest thing ever, if really difficult to photograph. I'm hoping that when my brother downloads his camera (which can do everything except play hopscotch), he'll have some good pix I can share.
The rest of the photos should be rather self-explanatory. Building with real tools, giant bubbles, vacuum tubes, wind tunnel, the best water table we've seen, and a marble machine that would do Rube Goldberg proud. We love it all. Plus, there are section set aside for the wee ones to play (and not get trampled) and lots of cozy nooks filled with relevant books to read.
If you have children 10ish and under, and you find yourself in the SW suburbs of Chicago, you really should visit DCM.