Happn.in is one solution to this problem. This site allows you to follow your local Twitter feed, see what the current trends are, and even advertise to the local Tweetstream.

Using the hashtag #hi_, the site allows you to find your location on a Google map (the sites currently covers Western Europe and the US), and click on the pin. A small window appears with a list of the current words that are trending, a “town crier” -someone from the area who has tweeted the most about the local events that week, the latest posts with the hashtag and a way to advertise to that particular area.

If you click on “More  [city] Detail” it leads you to a page where you can not only see what is happening, but Happn.in even lets you rate the tweets.

This information is already very valuable to marketers, and retailers. Happn.in has hit upon a formula that will lead to a lot of great data.

Twitter know lets you see what the trending topics are on your Twitter home page. However, many of us do not have a clue what these topics actually are.

What the Trend? to the rescue! This application (by Matt Mayer) explains what the topics are, when they started and the last time they were tweeted about. If you click on a trend, you can see the tweets, any news or photos (from Flickr) about the subject as well.

You can also follow @whatthetrend on Twitter.