There are clearly a lot of people on Twitter interested in information related to their location. And not just at the city level; they tweet and retweet about their suburbs, too. Take this feed, which is devoted primarily to things happening in (or at least related to) Wanneroo.
This is a goldmine for any business person keen to service a particular geographical area. You can get your products and services well known through Twitter for free. As well as the direct geo-targeted traffic it can attract, remember that lots of tweeps are also bloggers and webmasters, so you're bound to get a few local backlinks as well.
The key is to just to keep cranking out geo-specific tweets, and be sure to use the hash tags with the locations you cite.