Blogs, Groups, or Wikis?

I am thinking about this further and playing around with ideas.
I looked at Google Groups and created a group for my students.
I may go back to the Wikispaces site that I created a couple of years ago.
Maybe I will get my students to investigate all of these and see what they like best. I am trying to get them familiar with the Web 2.0 options available to them. By having them look at these options I am doing just that.
Next I will need to determine a way to assess what they have done in terms of Reading, Writing, and Media Literacy expectations from the curriculum.