Great lists so far... I've got nothing to add at this point, except for an appreciation of the zombie film genre. Pontypool was really interesting, to be sure. Dawn of the Dead remake was a great film, I get the sense that it helped inspire at least the visuals, if not the graphic novels for Walking Dead (or, if my sequence of events is off here, that there was some sort of symathetic relationship between the projects conceptions).
I love The Thing, but it doesn't really feel like a zombie film, except in the basest of psychological approaches (the stranger beside you, etc.)