I'm following the situation on several sites — Andrew Sullivan' Daily Dish, the New York Times Lede blog, the BBC and the #iranelection hashtag on Twitter. The Twitter hashtag is an unfiltered stream of information, and it's hard to know what's reliable, but the good stuff tends to get ReTweeted and picked up by the media.
I'm also following VPR's Steve Zind's Twitter updates. His latest tweet, from just before 9 a.m.:
"hard to judge reliability w/out knowing source of tweets or if 2,3 or 4th hand info. But numerous reports of clashes w/police. fog of war"
I found this photo on Twitter, and saw it on the NYT blog, too. The NYT attributes it to a blogger who is apparently posting from Iran. It's titled "Tehran 6/20/09"