This was an easy thing to accomplish in RoR… almost too easy.  Update your controller’s action to:

  def index
    @posts = Post.all

    respond_to do |format|
      format.html # index.html.erb
      format.xml  { render :xml => @posts }
      format.json { render :json => @posts }
    end
  end

The last format line is all it takes.  Bring up the page with the json extension: http://localhost:3000/posts.json

[{"post":{"name":"Post1","created_at":"2011-01-29T22:54:03Z","title":"This is Post 1 title","updated_at":"2011-01-29T22:54:03Z","id":4,"content":"Post 1 content"}},{"post":{"name":"Post2","created_at":"2011-01-29T22:55:25Z","title":"This is Post 2","updated_at":"2011-01-29T22:55:25Z","id":5,"content":"This is content for post 2"}},{"post":{"name":"dfasdf","created_at":"2011-01-30T00:36:36Z","title":"dfasf","updated_at":"2011-01-30T00:36:36Z","id":8,"content":"dfsdfd"}}]

That’s it.