Update: Treyarch has released a few descriptions of the new maps:

• Nightfire
  In “Nightfire,” players take to the streets of a war-ravaged Berlin with only the flames of the burning city to expose the enemy.

  Station
  “Station” offers a bombed out underground train station littered with hidden passageways and destroyed subway cars.

  Knee Deep
  “Knee Deep” takes place on the island of Peleliu in a once tranquil village turned chaotic Japanese command center.

  Verrückt (Zombie Asylum)
  The fan favorite 4-player co-op Nazi Zombies Bonus Mode returns with “Verrückt,” a terrifying Zombie asylum featuring more weapons, perks via the addition of Perks-a-Cola machines, electroshock defenses and the endless zombie horde.

Left 4 Dead wasn’t the only shooter to include zombie (infected) blasting fun last year. Call of Duty: World at War had Nazi Zombies, which was unlocked after completing the main campaign (recently it was unlocked for everyone). For those who are enjoying it, here’s some tasty news. In a forum post discovered by Kotaku, Treyarch’s community manager announced (on the forums) there will be more Nazi Zombie content in the upcoming World at War map pack.

Dear Alarmed Residents of Texas, Indiana and Illinois:

We hope that rumors of a new zombie level being included in the first Call of Duty: World at War DLC map pack wasn’t what sent you into a recent frenzy (http://www.kxan.com/dpp/news/Road_signs_warn_of_zombies). Nazi Zombies scare us too, which is why we’d like to give you a heads-up to stay tuned for official word regarding upcoming DLC. Yes, there will be a new wave of undead coming soon and – while we appreciate everyone’s concern (and we don’t condone vandalism) – we assure you that these zombies will only be found in the Call of Duty: World at War Map Pack. Stay tuned for more details!

Regards,

Your friends on the Call of Duty: World at War team.

Good thing Treyarch included Nazi Zombies in World at War because it appears to be well loved by the community. We’ll bring you more information on the upcoming COD:W@W DLC soon.