Aleister,
That’s the idea… but scheduled, rather than periodically.
eg: I have a category with hundreds of posts. That category gets one new post a day. For some time now, I’ve stopped adding new posts to the category though. I have enough posts to just cycle through them – one a day – and they aren’t repeated for over a year. It’d be nice if there was a plugin that just takes the oldest one and makes it the newest one. Options in your plugin might be: how often to change them, what time to change them, what category to affect, etc.
I think there would be many uses for this. My site would use it for daily devotions. Others could use it for helpful hints, words of the day, interesting facts, “from the archives”, and anything else that could be titled “Daily or Weekly ____ .”