Local. Social. Free. Useful.
HiNii propose cool places and new things to do. It's simple, just answer these questions:
With whom are you?
What kind of day do you want to spend?
What part of the day?
and view the itinerary generated
HiNii is opensource on google code: http://code.google.com/p/hinii/
AppBrain page: http://www.appbrain.com/app/hinii/com.angelo.hiniid