TalkToGather by Steve Chung

TalkToGather is a free messaging app, the first of its kind that integrates POIs to a messaging app and provides an event gathering function whereas the user can select a place and gather invites along with place info, a map, and other user tips. Additional features include sharing your favorite places and current location to other friends, adding reviews to specific places, and changing the color of your chat bubble!

Developer Website: http://www.posterous.com/talktogather