The Hidden Armies of Second Life
By one estimate from a leading member, roleplayers in the various Second Life military clans range in the several thousands, and count a couple dozen affiliations. (Some allied, others at a tentative truce, but many in fierce blood feuds.) Despite those relatively low numbers, the high attention to detail and the culture that's evolved around it is deep, detailed, and passionate. Via Nexii Malthus, here's a well-produced machinima from MJ Katsu that depicts one the leading militaries, Ordo Imperialis. Also: looks a bit like something Leni Riefenstahl would make, if the Axis was largely comprised of furries.