Twitter is interesting when looked at in a global sense, but even more interesting when you can delineate and narrow down what’s being tweeted. You can do that of course by searching, and more and more you can do it geographically. Twitter is helping that somewhat with their new “Local Trending” service, but unfortunately the sites that are getting local trends are somewhat limited.

Let’s back up a minute. Twitter’s “Trending Topics” are those keywords and hashtags that have become popular in recent tweets. It’s interesting to look at those trends in the aggregate, but as you might image trending topics in your area as a result of recent events — like weather activity, a conference, a concert, or something else location-based — could also be useful.

Trending topics show up on your Twitter home page. You have a “trending” partition on your right nav that defaults to global trending topics, but which you can change to a fairly limited number of areas — more about that in a couple of paragraphs —

Click on a trending topic to get a search result for that topic. (As far as I could tell, that search is a global search — your look at the trending topic is not limited to a particular geographic area.)

Twitter is “working on it” but at this writing has only a limited number of trending topic areas. Available countries include Brazil, Canada, Ireland, and the United States. Available cities include Atlanta, Chicago, New York City, São Paulo, and Washington DC.

Cool idea, but it’ll be a lot cooler when I can see trends for stuff that’s actually nearby!