I don't know many post-apocalyptic movies but one of the most creeping was The Day After Tomorrow. And the reason is.... because it can happen, well, maybe not that dramatic but it could happen in certain degree.
Another nice movie was The Happening... people just started to kill themselves apparently because of a chemical compound that was on the air, generated by plants. Also, I am legend was just... fantastic! Actually, that's one of my favorite movies lol
And what about equilibrium? you missed that one too
