Add a site-wide sidebar that holds navigation links
Create date-based navigation links. For instance, there would be a list of links with the names of the months and when you click on the month it shows you all the articles published in that month.
Track the number of times an article has been viewed. Add a view_count column to the article, then in the show method of articles_controller.rb just increment that counter. Or, better yet, add a method in the article.rb model that increments the counter and call that method from the controller.
Once you are tracking views, create a list of the three “most popular” articles
Create a simple RSS feed for articles using the respond_to method and XML view templates