At the end of the year, it's always fun to look back at the places you've gone and things you've done in the past 12 months, and if you log your comings and goings with apps like Foursquare or Twitter, doing that year in review is even easier.
To use Where Do You go, you've got to log in with your Google Account and authorize it to index your Foursquare check-ins, which gave me pause, since I keep my Foursquare history private. But, the app doesn't publish check-in details, just your past whereabouts in aggregate. You can delete all your data from the app if you want to just try it and bail. If you keep your account, the map updates with each new check-in, but only displays check-ins which are more than 24 hours old for privacy reasons. It's fun to see what areas of different cities you favor most—apparently I rarely travel above 34th street in Manhattan—and it can give you even more motivation to visit areas you normally don't, even in your home city. Someday I hope to get a similar heatmap view in ThinkUp for posts from Twitter and Facebook, too.