Here’s a complete list: http://www.top500.org/list/2012/06/100
Back in 2010 I was privileged to visit the system which is now #17 located in France. Our company, Bull, had just installed it. At the time it was at the top of the heap for European installations. These beasts are HUGE! There are so many cooling fans screeching that we were required to wear noise suppression ear muffs as we walked through the room.
We, at Bull, work with the folks from Lawrence Livermore Labs on the open software job scheduler used by a plurality of high-end HPC systems including the #1 system. The LLNL folks and a separate company do all the modifications required by the IBM BlueGene systems. The BlueGene optical interconnect is a really complex communications fabric which makes the scheduling requirements very specific to their architecture.
LOL - I've been in places like that. Matter of fact, I work in one - maybe not so bad, but bad enough!