Amid the confusion and accusations of Iran's election, the people of Iran are using technology to coordinate protests and voice their anger--despite the government's attempts to block their efforts.
The first sign that Mahmoud Ahmadinejad's government wasn't going to tolerate free-speech challenges to its position in power came in the run-up to the election--Facebook access  inside the country was blocked. But in the unrest following Ahmadinejad's claimed victory, Facebook--which was run from a dorm room just five years ago--remains blocked. Twitter has been blocked too, and unsympathetic Web sites are being barred. There are also indications that some cellphone networks are being interfered with, presumably under authority of the government, with text messaging apparently blocked across the country.
Renesys 's blog shows that in the days immediately following the election there was a significant instability in Iranian Internet transit. Outages weren't long-lived, and the blog states that Iran "remains well connected to the Internet" but it does note that "something (administrative, or physical) has affected Iran's connection to the submarine cables running east and west--not a total outage, but some kind of significant impairment."
Why is the government doing this? Because there is a significant question about the legitimacy of the vote results. A posting on Ehsan Akhgari's  blog sums up the issue well: By plotting the vote results for each candidate as they were announced over time, Akhgari notes that the results are a smooth curve. Given that different regions and even cities within Iran are more or less likely to support different candidates, that smooth curve seems unlikely--you would expect lumps and spikes as a particular candidate did better or less well than the others in particular results. Vote-rigging accusations are also founded on the fact that pre-election surveys indicated Ahmadinejad's main rival, moderate candidate Mir Hossein Mousavi, may well win the battle. His reported result of 34% of the vote seems to conflict with this data.
The government thus appears to be attempting to quell the national debate by controlling the technology people are using to communicate with each other. Facebook and Twitter are two obvious examples of a comms channel that's usually outside government control. The various images and videos of thousands of protesters on the streets , and of police brutality , are obviously uncomfortable for the incumbent president.
Despite all this apparent technological meddling, it seems as though the Iranian people are finding clever ways around government filtering. Several tweets are doing the rounds that give the addresses of proxy servers that are outside government control, and Ahmadinejad's main competitor, Mousavi himself, had been tweeting his protests until the government intervened. There was even a suggestion that people were using bit.ly to coordinate a DOS attack  on the country's supreme leader, Ayatollah Kahmeni's Web site.
And its just possible that this ingenuity has paid off. Ayatollah Khameni has just ordered  a totally unprecedented investigation into the vote-rigging affair.