Blog or Wiki?

A bunch of grad students in my department wants to set up a virtual space where we can exchange ideas, post documents, and organize events online. The forum does not necessarily have to be private, but we imagine that the stuff that we post will mostly be of interest to our little group. We are considering the creation of a blog or a Wiki. Which do you think would be better? Can you think of an alternative idea? Please note that most of us are not very tech-savvy. Thanks!