We threw the kids in the car this morning and headed out to the Boston Museum of Science. After a few wrong turns (stupid iPhone GPS), we arrived. The kids worked their way through every exhibit - what amazed me most is the way they were both able to enjoy the exhibits differently. Matt would be immediately drawn to what ever puzzle, computer, hands-on thing he could find and Molly would find the more involved problem-solving exhibits and read every sign she could find.
We had planned to spend the morning there and then head over to the Boston Children's Museum, as you can see from the picture of the outside of the museum - we didn't leave until well after dark.
We are already planning our next trip (which I am sure will include the Harry Potter exhibit opening this fall).