If you're on Twitter, set your location to Tehran & your time zone to GMT +3.30. Iranian security forces are hunting for bloggers using location/timezone searches. The more people at this location, the more of a logjam it creates for forces trying to shut down Iranians' access to the internet. Cut & paste & pass it on.
I'm not on Twitter, but I know a bunch of you out there who read this are -- so help throw a wrench in the Fundamentalist machine. There's not a lot we can do from here, but this one little thing could have a disproportional impact.