You may have heard about the Japanese magazine Science for Adults (Otonanokagaku), which recently came with a $30 analog synth kit. I'm now completely in love with the magazine, whose Japanese only website is full of wonders. There's a great little pipe organ - be sure to watch the video at the bottom of the page. The magazine itself looks great - page after page of stuff about organs, waveforms, and building the kit (you can even download extra punch cards). Admittedly it's not quite as elegant as this all-paper pipe organ, but it looks a bit more practical.
Gakken, their parent company, also produce many other great things, including these awesome electronics kits, which look like EMS synths.