I ran into an nice project, Rádio de Galena, a crystal radio that can be build by anyone, thanks to the brilliant way the circuit board is designed: just a piece of wood with an explanatory piece of paper on top. Website: Club S500.
Such a project brings back memories — an Amroh crystal radio was my first home-built radio. After that I was hooked. There’s a Dutch ham, Chris PE1DZX, selling similar kits at http://www.kristalradio.nl/.