Gowalla is a cool newish iPhone game from Alamofire (I love those guys). Here's the official blurb:
Gowalla is about going new places, doing remarkable things and meeting great people along the way.
I really enjoy using it. I took a small vacation with my mother to Denver, CO this week. We were hanging out in Estes Park wondering where to eat. I popped open Gowalla and found a nice little place to eat dinner. After we ate, we walked around town and got all of the other spots in Estes Park (I even created one).
Now I'm hooked. I have the urge to hit ever spot around me to get the stamp on my Gowalla password. I'm a sucker for points and achievements. Not to mention there's the whole items part, which is a lot of fun.