The folks behind RetailMeNot have built Trendsmap, which takes Twitter posts and related content and locates them on a map according to (if I remember correctly) the location of the user posting the content. They said they’ve incorporated about five million Tweets at present.
You can zoom in to the city level, but as Twitter geocodes Tweets they say they’ll get down to the neighborhood level potentially.
In the upper right module, which shows the posts, you also get related video and images that have been linked to from Twitter.
This was just a side project and there’s no business model or monetization plans. But one could easily imagine news organizations (online and on TV) wanting some version of this to display. It’s not unlike what MetaCarta is doing with newsmaps.