The open source augmented reality server, or POI (Point of Interest) search. In its simplest form, it takes a database of points with latitude/longitude, and a search request at a given latitude/longitude, and returns the points sorted by distance.
Minerva is a multiplatform framework that provides a high level language to specify Augmented Reality applications in a very easy way, equivalent to Blender GameEngine. More info, please visit theminervaproject.wordpress.com
Project mARbleMaze is an augmented reality minigame where the user uses a printed marker and his webcam to solve marble maze levels. Levels involve special fields like invisible walls and holes.