A Pi-Powered Plan 9 Cluster
While this looks cool it is far from useful. I took time to build such cluster with the Pies and shortly after it landed in the box of things I may need in the future. It's just too slow to do anything useful. Watching stuff compile or even boot was like watching paint dry. It is much better to get a bunch of used NUC if you are space conscious or just get VMWare Workstation or similar tool to simulate number of machines on your desktop.