What is the ruling on calling for a "Million-Man Fajr Prayer" campaign on the first days of the Third Islamic Intifada, and publicizing it in mosques and public squares, along with mentioning the details and goals of the campaign?

The action mentioned in the question is good due to its effect in reminding people of the Fajr prayer and encouraging its observance, and in reviving its preservation in mosques. This falls under enjoining good, with the caveat that the call to gather for Fajr prayer should not be specific to a certain day, but rather a call for its constant preservation. This should be accompanied by diligent efforts to remind people of the virtue of congregational prayer in general, and Fajr prayer in particular, clarifying that neglecting it was a sign of the hypocrites, and disseminating texts that encourage this at all times.