In two primary schools in The Netherlands we examined semi-plug 'n play materials that you can put to use in the classroom. Such materials contribute to knowledge construction rather than just knowledge transfer.
We already have intoduced (among others): Lego Robot Turtles, the Bee-Bot, Moov, MaKey MaKey; and even the more technical stuff like Arduino Tinker Kit, Sparkfun Inventors Kit, and Kano-box. These are supplemented with books like '50 Dangerous Things You Should do with kids.' All of this provides a base for many instructive hours of fun.
Together with the two schools, we looked for ways to implement the materials in the curriculum. What we were aiming for is that the pupils are going to investigate themselves how the materials work, what you can do with them and how you can share the knowledge gained with others.