It appears that a bunch of computational engineers, lead by Professor Simon Cox (the full team is acknowledged here) at the University of Southampton have built a supercomputer from 64 Raspberry Pi computers and Lego (yes, you didn’t read wrongly. Lego).
The supercomputer is named “Iridis-Pi”, runs off a single 13 Amp mains socket and uses MPI(Message Passing Interface) to communicate between nodes (using Ethernet). The entire system apparently cost under £2,500 (excluding switches) and has a total of 64 processors with 1Tb of memory (16Gb SD cards for each Raspberry Pi). The free plug-in ‘Python Tools for Visual Studio’ was used to develop code for the Raspberry Pi.
Interested in building your own Raspberry Pi Supercomputer? Well, the full documentation and guide can be found here.