In Teheran, they're burning petrol stations in protest at new rationing. The common people are understandably pissed at President Ahmadinejad, who has made an utter mess of handling the nation's economy (unless you happen to be one of his cronies, in which case you're doing just fine). The situation is being helped along by sanctions on imports, which the U.S. describes as a "point of leverage", as Iran has lots of oil but little refining capacity and so must import the majority of its refined petrol.
There are lots of rightwing American bloggers on the subject today. Most hope that the violence will get worse and that the Iranian regime will then fall. My reading, though, is that they're forgetting - as they do so like to do - that Ahmadin-nutjob is a term limited first minister, not a dictator in perpetuity. He's up for re-election in 2009 and at that point he's history. However, since the regime as a whole can blame him and remove him, it isn't going to fall.