OpenSocial is of course the Google-led consortium of competitors to FaceBook, but until very recently most of its efforts appeared to be vaporware. This is starting to change.
One of my immediate concerns about the OS API was how easy it would be to build an OS compliant container. Otherwise, we would have to rely upon existing containers (Orkut, anyone?) to host our OS-based applications. Fortunately, the Apache Shindig incubator project (http://incubator.apache.org/shindig/) is something of an open source reference implementation for the OS API (written in Java with a Maven build no less).
Check it out with SVN and build from source with Maven (worked perfectly on version 628525). Run with Jetty server.
Point browser to http://localhost:8080/gadgets/files/container/sample1.html and look through other samples. You can also load these HTML files using file:// if you don't want to run the Jetty server.
Next time: can I use OS clients to query my LinkedIn profile?