GeoPress is the world's first entirely OpenSource Geo-Tagging Platform....
Install GeoPress on your own server, create maps, places and start checking-in. You can create both private and public places, leave full HTML content for both checkins and place descriptions.
However, please note that at present, GeoPress is in an EXTREMELY alpha state. It has been released now to the public not only as a way to demonstrate what is possible with BackPress - http://backpress.org - but to more importantly get people to start thinking about the importance of such a platform.
These details are provided for information only. No information here is legal advice and should not be used as such.