To see this tool in action, visit http://krofdrakula.github.com/microdata-tool.
This tool was written to aid in debugging and browsing HTML5 microdata.
To use this tool, simply include the script anywere after the inclusion of the jQuery library. When you view the page, a list will appear in the bottom left listing all the microdata objects detected on the page.
This tool is a work-in-progress and still doesn't adhere to the full specs (yet). Plans to support the full microdata spec + data vocabulary validation are on the drawing board. ;)