I decided to see what I could do with Node.js today. I've never used it before, but understood the concept of it. It was really nice to work with, I didn't tear my hair out too much, and after a few hours learning some really basic Socket.IO stuff by making a web chat room, I tried this.
This Twittery-Nodey-Sockety-sort-of-thing uses ntwitter to stream tweets from the Twitter Streaming API, and pipes them through to clients with Socket.IO. It all runs quite nicely on Heroku.
It currently attempts to stream all tweets that have coordinates in them, and the page displays the latest 100 at any given time, removing them as the queue fills up. Each marker has a tooltip that displays the tweet text.