Thanks for the ideas, everyone. These are great! My budget is pretty low but I'm seeing some things here that might be great for now, and some others that we can build up to.
We do have the Magic School Bus science kit subscription already, though we've only gotten the first kit (the water experiments).
EmeraldCity, some of those look quite cool. We were in SF this summer for work+vacation and my daughter got to go to the Exploratorium with a local daycamp, but DS was too young for the same camp and never got to see it.
I don't know if it's still there but that Tinkertopia place puts me in mind of a place we went to in Edmonds when my daughter was in preschool. I don't know if it's still there. They just had a lot of totally random parts 'n' stuff you could make things out of. I have no idea what it's called or if it's still open.
