Encarta, Carmen Sandiego, Kids Typing, and Gizmos & Gadgets. It was the perfect confluence of events - I spent hours of time on these and might have actually learned something.
Slightly related, in Junior High, most boys in my class knew absolute zero − 273.15 figure by heart as if we discovered it and we got it from Saint Seiya. Used well you can convey extremely strong knowledge to young kids.
