In my area there’s a website called IndyBay. It’s part of a media apparatus that emerged in the aftermath of the 1999 World Trade Organization protests- something the activist left routinely refers to as the Battle of Seattle. The traditional media reaction to the protest, including a damaging accusation by the New York Times that protesters had used Molotov cocktails (which they had to retract) led to a shadow media devoted to organizing and defending activism.
There is a calendar where people can put up vigils, marches, or lectures. Some are important and straightforward- the Berkeley UU congregations post up their events, for instance.
But there’s a less colorful side of it. There are marches ostensibly to protest various injustices; a year ago I went to a march in Oakland in the aftermath of the Treyvon Martin shooting. However, they’re an illusion of sorts- the issues draw a diverse group of people in, but the event is actually more of a seminar for a political party.