The Earth Simulator supercomputer retains the number one position with its Linpack benchmark performance of 35.86 Tflop/s (“teraflops” or trillions of calculations per second). It was built by NEC and installed last year at the Earth Simulator Center in Yokohama, Japan.Here is a short list of the five fastest supercomputers :
The list of cluster systems in the TOP10 has grown impressively to seven systems. These systems are built with workstations or PCs as building blocks and often connected by special high-speed internal networks. The number of clusters in the full TOP500 grew also again strongly, now totaling 208 systems up from 149 six months ago. This makes clustered systems the most common computer architecture seen in the TOP500. The importance of this market can also be seen by the fact that most manufacturers are now active in this market segment

The full list with all 500 supercomputers can be found here