Zombie Panic! Source Zombie Servers

What is a Zombie Panic! Source zombie server?

One round starts with everyone human and one or two players picked as the first zombies. Infected players convert the humans they touch, so the human team shrinks all round while the zombie team grows. Humans win by surviving to the timer; zombies win by turning everyone.

Most of these run the Zombie Plague mod or a descendant of it, which adds an ammo-pack economy, class choices and unlockable extras on top of the base game. Expect barricading in a corner with three other humans, a shop menu bound to a key, and levels that persist between sessions on the servers that keep stats.

This is a short list — 2 servers on Zombie Panic! Source at the moment. The full Zombie Panic! Source list is a better place to start if none of these fit.