We are huge believers in educational toys. Here are two of our favorites:
For small children, you can't beat this lock box. There are several brands out there, and not all are so expensive. Watch out, though... Your little one will soon be able to open every latch in the house! I score it 10 out of 10.
Here is a circuits toy that a friend gave us. It snaps together like electrified Legos, and each piece has its proper symbol on the top. That way, the plans are actual circuit diagrams. Snap the modules together to match the plan, and the light comes on.
The only drawbacks to this toy are the small sizes of some of the blocks (easy to lose) and connections that get loose over time. You need to be somewhat gentle with it. I'd score it 9 out of 10.
We are big on "affordances." We try to give kids the mental and physical leverage to do more than they could alone. One of my fondest images of parenthood is a toddler with a step stool in her hands and a determined look in her eye. A great educational toy makes abstract concepts like circuit diagrams easy and obvious. (And fun--it's a great day when the kids beg to do more math homework...)