You can now wire-in external datasources to Google’s Visualization API (see announcement). Previously, you had to populate the various UI widgets from Javascript or from Google-hosted datasources (such as spreadsheets). Their examples page shows some of the possible visualizations. My favourite are the Motion Charts, based on work acquired from the wonderful GapMinder project.
OpenSocial’s API reference describes a number of classes (‘Person’, ‘Name’, ‘Email’, ‘Phone’, ‘Url’, ‘Organization’, ‘Address’, ‘Message’, ‘Activity’, ‘MediaItem’, ‘Activity’, …), each of which has various properties whose values are either strings, references to instances of other classes, or enumerations. I’d like to make them usable beyond the confines of OpenSocial, so I’m making an RDF/OWL [...]
From the opensocial-api group, an OpenSocial Javascript API priorities document. “This page contains the updated priorities (in draft) for the next iteration (version 0.7) of the OpenSocial JavaScript API.”