Annalee Newitz has a quick primer on zombies over at io9. It ain't bad, but I have to push back a bit against her use of the word "first" while discussing this sequence from White Zombie (1932):
This was the first cinematic zombie moment in America. Not only are these shambling zombies pretty instantly recognizable, they are also entirely connected with imagery of slave labor and African-Caribbean culture. Zombies are black slaves.
There is indeed a close connection between slavery and cinematic zombies. But those ties go back at least 17 years before White Zombie. D.W. Griffith's racist epic The Birth of a Nation, an enormously influential movie released in 1915, climaxes with a mob of former slaves attacking some whites who have holed up in a cabin. To quote myself, "If you've seen any modern zombie movie, then you've seen an echo of the cabin scene: In Griffith's eyes, the blacks outside that little house are the Living Dead, their monstrous arms reaching through the doors and windows while our heroes try desperately to fend them off."
See for yourself. Birth of a Nation is streaming at Netflix; if you watch it there, the heart of the sequence starts at the 3:00:35 mark. If you aren't a Netflix subscriber, you can go to the crappy-looking version of the film posted on Google Video, where the scene starts at 2:53:51. The most Romeroan moment is from 3:02:17 to 3:02:21 on Netflix, from 2:55:31 to 2:55:35 on Google. When Night of the Living Dead flipped the scenario around—offering a story in which, as Newitz puts it, "a black protagonist has to deal with hordes of white zombies"—the picture didn't just reverse the classical zombie tale. It reversed one of the films that created Hollywood as we know it.