Are poeple the only creatures that can be zombies? Is it possible to have zombie dogs or whatever?
According to http://www.religioustolerance.org/voodoo.htm:
I would assume non-human animals could be drugged and then revived as well.
Although: “a person believed to have been raised from the grave by a houngan [sorcerer] for purposes of enslavement. The zombi is used by his master to perform heavy manual labor and to implement his evil schemes.” (encyclopedia.com) The zombie’s soul has been co-opted, which is probably not possible for a non-human, but that’s a Great Debate. 
According to Zombies and Voodoo Trivia Quiz, people are made into zombies for “breaking specific social rules”; I’m not sure how this applies to animals. Peeing on the carpet hardly seems punishable by zombification.
Wade Davis won some notoriety for his book The Serpent and the Rainbow, in which he suggested that zombification was the result of paralyzing the person using tetrodotoxin, then “raising them from the dead” in a sort of drugged/hypnotized state. (The book was later made into a movie by – I believe – Wes Craven. This makes it the only anthropology book that has been filmed by a director of horror movies. It makes you wonder if they could draw audiences into a film version of “Coming of Age in Samoa” was directed by, say, Sam Raimi. But I digress…)
If being a zombie requires some sort of hypnosis, then I seriously doubt you could do it to a dog. A zombie dog wouldn’t differ in any wat from a non-zombie dog. Zombification would seem to require intelligence and imagination on the part of the victim. By those criteria, you shouldn’t be able to zombify some people I know.
Cecil also wrote about zombies: http://www.straightdope.com/columns/990521.html