The Manhattan Project
A city of vampires is usually comprised of some combination of 1 to 5 of the following factions, called Covenants. Each covenant usually contains members from all clans.
Carthians are social scientsts who base their governmental structures and policies on advances made by human society.
The Circle of the Crone is a group comprised of small isolated religious cults, generally venerating some incarnation of the Maiden, Mother, Crone trinity.
The Invictus are also known as the First Estate and are primarily concerned with maintaining material wealth and power.
The Lancea Sanctum are also called the Second Estate, or the Longinians, and their beliefs tie heavily into monotheistic faiths.
Last, but not least, the Ordo Dracul, also called the Order of the Dragon, or the Dragons, is comprised of scientists and the desperate.