If you're not a cryptography or World War II nerd and you know anything about the Enigma machine, chances are you've read Neal Stephenson's novel Cryptonomicon, in which fictional characters work alongside historical figures like Alan Turing to crack the Axis codes and sink Nazi submarines.
Designed as a project to raise funds for museums, the Enigma-E DIY Building Kit is £119.99 from Bletchley Park and €130 from the Museum Jan Corver and comes with every component required to assemble machine. You will need basic soldering skills and some knowledge of electronics to figure out the circuits though. If that's too much money or too much technical know how, you can always try out the Paper Enigma Machine.
Enigma-E DIY Building Kit
Enigma-E Kit [Bletchley Park Shop]
Enigma-E DIY Building Kit (scroll down) [Museum Jan Corver]
Enigma-E: Recreating The Infamous Nazi Code Machine Electronically [Retro Thing]