Iran, Iran, Iran
Ok, the important shit that's happening today is obviously Iran.
Though I'm no big fan of Mousavi, I am a big fan of popular democratic resistance movements to authoritarian quasi-democratic states. If this can lead to actual democratic Change in Iran, I'm all for it, especially since this appears to be a precipitous outbreak of anti-authoritarian sentiment.
If you are way behind and want to catch up fast, I suggest the rapidly-expanding Wikipedia page. Very unstable, but gives a good summary of events. Then, move on to the Wikipedia page covering the protests.
After you're done catching up, Twitter provides mountains of raw data, and heaps of links and coordination. It appears to be down or groaning under the strain right now. I'm guessing – completely guessing, not a rumour you should spread! – that Iranian hardliners have launched a DOS attack on the Twitter.com racks. The place to watch is the #iranelection tag.
One of the big pieces of news for us social media nerds this evening was that according to Reuters, the US State dept. has been talking to Twitter management in order to get them to postpone scheduled downtime. The intention was obviously to keep the dissidents able to communicate. This means that the US is – very quietly – taking sides for the dissidents. It is very clever of them that they don't undermine the movement by giving it the impression of being USA-backed. If this runs its course, the US gets the first step on the way to where they want Iran, the dissidents get to keep their aura of grassroots, local change (an aura that reflects their real nature, as far as I can see without leaving my chair) and the people of Iran get a new, less authoritarian system of government and a revitalised public sphere, human & women's rights and labour movement (I hope, I hope, I hope).
A link that has generated a lot of attention is Esko Reinikainen's blogpost on cyberwar, which is now down due to bandwidth or a Denial of Service attack (bonus synchronicity: I happen to sorta-kinda know Esko Reinikainen from a completely different setting). There are many mirrors, many of which can be accessed from the comments of this page. Also French and German translations down there.
Also, Andrew Sullivan of the Daily Dish over at the Atlantic has been blogging on Iran non-stop and appears to be on top of a lot of things. A lot of raw data there too, as well as analysis.