Not being a fan of Foursquare myself I have found many of the auxiliary apps to be just as useless except the ones that provide something of value beyond an ego-centric “look-I-exist” mentality.
(There aren’t many of them, mind you.)
But, I think I found one:

Blacktop lets you organize your Foursquare and Facebook check-ins into “trips” that you can share with your friends.
It’s a great way to tell the story around a vacation, a day trip, or a night on the town.

I could actually find this interesting and useful. Way to go Zenbe for making Foursquare useful!

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