I had to do a few simple things. First, I had to edit environment.rb, adding a definition for config.action_controller.session. Actually, Rails will warn you about this and tell you exactly how to do this. I also had to run two commands because Rails has been made more modular:
script/plugin install auto_completeI have been making my web apps (Rails, Java, and Common Lisp) more "RESTfull" in the last few years and the Rails 2.0.x REST focus was enough for me to decide to update sooner rather than later.
script/plugin install acts_as_list