I've read the documentation page about upcoming Joomla 3.3 Microdata http://docs.joomla.org/Microdata
It sounds Ok.... but how can a user implement it in a simple articles-loaded-by-user site?
Actually, Joomla 3.3 will have it hardcoded in the layout files, because it's just not easy to use by the user. There is a GSoC project to make the library more user friendly.
Also, JCE has included a microdata editor plugin that may be useful in the meantime.