Google+ users interested in doing some preview-testing of upcoming Google+ features, might be interested in the Google+ Platform Preview Group. This is a Google Group which, when joined, will make your account view some Google+ things earlier than others. As they put it in their description:
Subscribe to this group if you would like to preview the latest updates to the Google+ platform (such as to the +1 button) before they are launched to the general public. New features will be enabled on your account and announced to this group. You must use a Gmail address for the preview to work.
Obviously this may put you at risk of having slightly broken content, something you should always keep in mind when being part of a test group (eg alpha/beta releases etc).