The root cause of the problem has been identified as a change in some core CiviCRM code that was incompatible with how a common plugin interacted with member syncing to WordPress, and a temporary patch has been applied. New registrations seem to be working again.
Apologies for the inconvenience. If you signed up in the past couple of weeks and never got a signup email, please try again. If you are still having problems, drop us a note with the contact form in About Us and we will look into it when we can.
Thank you.
