What you're describing reminds me of the Mathic system in Neal Stephenson's book Anathem. The characters are sequestered in groups defined by the interval at which they interact with the outside world.
There's a good summary of Mathic life at http://anathem.wikia.com/wiki/Mathic_Society (the site contains spoilers, but that page looks safe to me).
Though not configurable, the "Top Links" feature does something like this:
http://news.ycombinator.com/best
It's really useful, but it's somewhat obscure since there's no link to it from the main page. (You can find it under "Lists" at http://news.ycombinator.com/lists)
This reminds me of the project SlowMail
i only could find the cache: http://bit.ly/c9dWWF
Don't use shortened URLs here, please. This isn't twitter; post the full URL.
The url goes to a May 20, 2010, google cache.
Why? [edit: Okay, I didn't see that he could only find the cache. Just for future reference doron, at the top of the webshot is displayed the URL.]
Here's the URL unshortened and uncached: http://www.slowlab.net/slowmail.html
I know, the web-server did not respond at the time of posting, that is the reason why i posted the cache, and therefore didn't see the reason to post the full URL.
The key is to use a ranking procedure that is appropriate for the interval, so that the reader doesn't get new stuff for that day, but the best over N days (or N seconds -- not everyone is Richard Stallman).
This feature may be silly and unoriginal; but I'm commenting on the internet so I thought it fit.
[Edit: when I said "delivered" I didn't mean by email! Just "updated".]