According to Top500, the world's most powerful supercomputer Tianhe-1A peaks at, if I'm reading this correctly, 4701000 Gflops, or 4701 Tflops, or 4.701 Pflops.

Here are current Folding@Home stats:  9259 Tflops, or 9.259 Pflops

BOINC is 5380 Tflops, or 5.38 Pflops

And...  Bitcoin Watch shows the network hashrate at 53547 Tflops, or 53.547 Pflops.

That is an amazing concentration of computing power -- and it's still growing.

(this thread illustrates how bitcoinwatch arrived at those numbers)