If you like George Romero's zombie flicks, you would love "28 days later" It is a movie that just came out on DVD. It is a UK film about a super virus that kills off most of the population of London. It is a much updated version of Romero's works, and not quite so cheesy (Although I loved all his films) In this movie, the "infected" while zombie like, are not undead zombies, but rather humans that have been infected with a virus that causes them to go into a homicidal rage. They dont eat brains, and they dont walk slowly after thier victims, in fact, they run quite fast. They are just raging lunatics looking to kill everyone in site.
A large portion of the film is shot in an urban environment and the survivors are left living off of vending machines and collecting water in buckets atop buildings. Lots of improvised weapons as well. All in all, a good flick. Search google for 28 days later if your interested.