A cool toy that got my 4yr-old hooked. Actually I've got only the first 20 pieces from a local store to see what's his reaction, the best deal is from the web: http://www.toymagnets.com/supermag/index.cfm.  

I think we'll try an IcosahedronImplementation.

A nice picture: 

http://www.toymagnets.com/images/supermag/eiffel_large.jpg