I used to come here on field trips as a kid, and I went back recently for the first time and it was just as fun! They have an impressive number of hands-on exhibits that deal with all aspects of science: plants, animals, genetics, physics, chemistry, etc. It's a great place to take your kids as they'll learn a ton and have fun doing so too. I loved the shadow box and the oversized bubble makers when I was a fourth grader, and was happy to still see both things still around.
There is free admission on the first Wednesday of the month.