I probably liked 90% of the films listed in this thread. The Road, perhaps too scary, considering the flesh eaters are actual live humans. I did love the film though.
Day of the Dead is an awesome choice, if you mean the original. I thought the remake was total garbage. Dawn of the Dead was totally different story. I really liked the original, but I loved the remake. Ving Rhames, badass.
I recently saw two new additions to the "Dead" series(Night, Dawn, Day + Land of the Dead): Diary of the Dead & Survival of the Dead. Both are low budget, but directed by the master himself. I thought the Diary of the Dead was excellent, Survival, which I bought on Blu-ray, not so much. Survival of the Dead just came out on DVD/Blu-ray Tuesday.
I'm braindead right now, and I can't think of many recommendations. Maybe the TV Series Lost, or if you don't mind a dumb comedy flick, Eight Legged Freaks. If you like zombie flicks, it is criminal not to have seen the Return of the Dead(sucks after Part II though). Ghosts of Mars? One of my favorites, considered by many to be garbage. That's about it. I almost forgot about Infestation(really good "B" comedy flick), I also liked the remake of The Crazies. Original, not so much.