Some neat hobby kits from Japan include a working vacuum tube radio (see an assembly video here) and an Edison-style phonograph kit that actually lets you record your own voice on a plastic cup!
If you're looking for a fun and easy educational electronics/science kit for a young relative (or even a toy for yourself), a Japanese toy and hobby site called HobbyLink Japan offers some interesting products. I found out about the site recently when I ran across the following entertaining short video (5:57) showing the assembly of one of the company's vacuum tube radio kits - a "nostalgic style" regenerative AM receiver complete with plastic horn speaker - and how it operates:
I went to the site to find out more about the vacuum tube radio kit, but it appears to have been discontinued. However, I found something just as interesting - a new "phonograph kit in Edison style" that apparently will actually let you record your voice on a plastic cup for up to 50 seconds! It looks like a pretty neat toy for $26.48 USD.
BTW, on a related note to the radio kit mentioned above, Bill Schweber of Planet Analog has an interesting column this week - "Thinking superhet thoughts" - on the superheterodyne receiver architecture and its inventor, Major E.H. Armstrong. Armstrong also invented the regenerative circuit used in the above radio kit, although, as Bill Schweber notes, subsequent patent disputes ultimately granted the patent to Lee De Forest - widely credited with the invention of the vacuum tube.