One particular example that showcases a unique service - although it's not done in a digital marketing sense - is #uksnow at http://benmarsh.co.uk/snow/
We all know that the UK has been suffering severe snowstorms this year. In fact, it is the worst in 18 years. Twitter users in the UK have been tweeting about this weather so Ben thought of combining Google Maps with Twitter posts to create a Twittermap of the UK snowstorms!
It's a simple idea: Ask people to hashtag their Tweets with #uksnow, put in their geo information, and add a twitpic if possible. Voila! Those tweets feed into the Google map. These realtime tweets allow users to see how the weather is at several parts in the UK. Even a million-dollar telescope can't do that because of severe cloud conditions. That's a unique service :)
Here're the exact instructions on the site:
Tweet the first half of your postcode, and rate the amount of snow that is falling out of ten (0/10 for nothing, 5/10 for steady snow and 10/10 for arctic blizzard conditions) >> "#uksnow [FIRST-HALF-OF-POSTCODE] [SNOW-SCORE]/10", ie: "#uksnow NG9 3/10".
Add your twitpic url to the end of your tweet to show it on the map >> "#uksnow [FIRST-HALF-OF-POSTCODE] [SNOW-SCORE]/10 [TWITPIC-URL]", ie: "#uksnow NG9 3/10 http://twitpic.com/aaaaa".