Browsing io9 this evening I happened across a wonderful interview with Jesse Eisenberg (Columbus), and Paul Wernick and Rhett Reese, the star, and writers of Zombieland respectively. If you haven't seen the movie yet, do not read this interview, however, do go see the movie immediately. If you have already seen the movie, you should find this interview interesting. They talk about the death of the celebrity cameo, which was brilliant, and all the other celebrities considered for said cameo. Very intersting...
Additionally, there's another interview with the writers about the original plans for Zombieland. Apparently, it was originally written as a television series, and in its movie incarnation, you're seeing the first two episodes. Meaning, if there were originally 23 episodes planned, there's enough story left for many more Zombieland movies. Just imagine all of the hilarious possibilities!