OpenLBS - Open Source Tracking
I've just finished working on the initial release of OpenLBS. OpenLBS is an open source suite of location based software. The two initial components of the project are the client and the server. The server is Pylons-based project that implements the OpenLBS HTTP Specs. The client implements those same specs to work with the server.
OpenLBS is useful if you want to run your own tracking server, or if you want to customize it according to your needs.