We have a build of an Applet that will assist in the removal of older versions of the JRE. The Applet is available for testing on http://java.com/uninstall-tool . At this stage the Applet only targets the Windows platform, as it represents the largest installed base and the need for platform specific elements made Windows the logical starting point. We are deliberately not giving documentation on how to use the applet - we want feedback of the tool standing on its own.
The intent of making this build available is to gather feedback; ideas, suggestions, comments, good and bad, what works, what does not work, what could be improved, etc. Please try it out and give us feedback to ensure a smooth release.
Roger Yeung in a post with more details on providing feedback.