Beth Kanter has an excellent overview of recent discussions on how nonprofits and NGOs, mainly in the US, are using online video sharing sites, and also experimenting with their own vlogs documenting their activities.
Most examples so far seem promotional or fundraising-driven rather than advocacy-driven, and its not yet clear how traffic is being driven to see their posts on Youtube etc, but this can only be a matter of time.
What are you seeing from your perspective?