This is an olde post, that I'm coming back to, and adding onto. Two interesting uses of twitter:
1) Twitter as Subject Stream: Over on techcrunch there's a post about how Quora is using Mechanical Turk to automate the creation of twitter accounts. Quora is a mass Q & A website for anything. You ask a question: "Where's the best place to crowdsource an icon?", and you get a response, for example from user alton sun :"99designs.com….".
Quora the site is organized into many subject areas which you can subscribe to (UI, Startups etc.). They are creating a twitter account for each of these subject areas, so those interested Quora users can subscribe to the feed and get the newest message from that subject area. It's cool.
2) Twitter with a High-Pass Filter: This is the newer part of the post, Jeff Miller, has created a twitter feed that broadcasts Hacker News stories when they reach a certain point value. http://twitter.com/newsyc100 was the first one I noticed, it broadcasts stories once they reach 100pts. But it seems he also set a feed with 2opt, 50pt and 150pt triggers. I really like the idea that once something has reached a level of community interesting-ness—as manifest in points—you can grant Hacker News the ability to become a verb and reach out and tell YOU about it.
You can decide that anything that is of n interestesting-ness to a community is of interest to me.