Right now, 186THash/sec
http://bitcoincharts.com/bitcoin/Unfortunately FLOPS are not a good metric for bitcoin hashing as its intrinsically an integer operation, rather than floating-point. Perhaps the hardware comparison list is a good place to start
https://en.bitcoin.it/wiki/Mining_Hardware_ComparisonLook at the hash rate for a typical CPU and scale it up to the full network hash rate. So a top range intel processor give 5MHash/s per core. which equates to 37 million cores (or 9 million quad-core processors) for the full 186 THash/sec. Of course nobody mines with CPUs these days as GPUs. FPGAs, ASICs all give (in order of magnitude) far greater performance per dollar/watt/joule metric.
If you want to compare with the top 500 supercomputers (20 PetaFlop leader), its difficult as the Petaflops tell you nothing about the integer performance. Hmm, getting out of my depth here, I guess the integer performance figures are out there somewhere, and then its a matter of scaling up vs a known CPU hash rate. Oh well, maybe experts will chip in, they do haunt newbie land from time to time. And since I've made the effort to write all this, I'm going to post it anyway. Push.