Current featured article: Super Mario World 2: Yoshi's Island
List of all featured blurbs: Category:FeaturedBlurbs.
To add articles, just add them to the list and increase the last Modulo operation by the number of articles you added.
This will change content at least every hour. If the seconds are uneven while the site is being cached, it will add the seconds as offset to the hours, else it will add the current week and 3 for randomness. Remember, this is time of caching, so it has to be done at least once an hour.