In August, Google released a field trial allowing Google search users to include their emails in their Google search results.

There was a lot of privacy backlash, so Google kept saying it was opt in and there are privacy controls. So Google waited for the steam to calm down a bit and now said on Google+ that this field trial is now open to more Google users.

Google said:

Google Apps users are still not able to participate but everyone else, sign up over here.

Forum discussion at Google+.