It's mostly on behalf of a particular cause. For example, somebody might organize the community to help set up a neighborhood watch. Another for protests. Another for religion related stuff. A community organizer is not a bad thing. I love how some have tried to turn it into a dirty word.
You only find community organizers in the inner city. We all know them as race pimps and whores. They get a bunc of people all excited about how 'da man is givvin' thenm the shaft, then go down to City Hall and get on the microphone and threaten "do things my way or we will react violently."
Jessei jackson is a community organizer. al sharpton is a community organizer. the weather underground were community organizers.
And even if community organizer wasn't an epithet, being one does NOT make one ready for the most important job in the world. As Governor Palin said (paraphrasing), "community organizer" is like an elected official with no responsibilities. That statement can not be challenged.