TwitterLocal tell us that Twitterlocal lets you generate an RSS or XML Feed to filter out Tweets around a certain area. Just enter a city, state, postal code, choose the range of miles you want to include, and hit the button. You’ll instantly get URLs to add to your RSS reader.   Worth a try if you want to find local Tweeters!  

http://www.twitterlocal.net/show/Berlin%2C+Germany/5