Distributed computing's  most public face , to date, has been Seti, the search for extra terriestrial intelligence.  Basically you get a problem that relies on intensive number crunching and then farm out the computation to many systems which, in their down time, work on  tiny parts of the problem  and then send the info  back to a central location.

The Germans ( don't mention the war)   possessed a portable cryptographic  device , commonly known as the enigma machine which due to some fortuitous happenstance the allies managed to break , most , of the messages intercepted. Several messages have surfaced , one of which has already been broken by The M4 Project  who are using distributed computing to decipher a few messages that have until now  help the secrets to the Fuhrers Niemann Marcuss cookie recipes, er who knows.