Stateless Systems, the creators of BugMeNot and PDFMeNot, have a new tool called Trendsmap that hasn't been designed to solve any productivity problems. Instead, it does just the opposite and serves as entertainment. It tracks trending Twitter topics by geographical location by combining data from Twitter's API and What The Trend. It then sticks it onto a Google Map where users can sort by city or general region and see trending topics in real time.
All of this information is organized into something resembling a tag cloud, which floats around without any specific, or pinpointed location within each city. Clicking on any of them pops up a small info box that aggregates the latest tweets, local and global seven-day histories of that trend's popularity, as well as some top-related news links that change depending on what's trending.
Where the site shines though, is in letting you dig even deeper by giving each city its own trends page. Here you can cruise through info boxes without first having to find each tag, as well as see all of the trending charts stacked up against one another--something I think makes for a better experience. It also collects all of the related media like photos and videos in one single section (try giving it a spin for Las Vegas).
One thing the service doesn't do very well though, is serve smaller towns. This wasn't a big deal killer for me since I'm based in San Francisco, but if you want to use it for somewhere that's outside a major city, you're out of luck. This may simply be a limitation of how deep the data set is, but it keeps you from seeing trends starting up in smaller towns, which can be more interesting than in major cities.