Wiki wiki blog blog

As I bounce back and forth between the wiki that I have to edit, this blog to check comments and post new thoughts, and other blogs that I am watching...it is hard to believe that I am actually doing this! Just a few weeks ago I didn't know what a wiki or a blog was! Now I am involved in creating, commenting, editing, and reading both! In the next few weeks I have to create a lesson plan using a wiki or a blog. I have ideas for both, but don't know which would be the best to use for my first lesson with high school students. Do you have any ideas? Suggestions?