You can give people access to the Diary who are not registered MultiMe users via a secure URL access link sent out via email.

NOTE: Email access link users will not be able to edit the Blog section of the Diary, in order to add to the Blog they will have to register as users. By selecting the 'Invite to Register' option you can send them a link to the Diary and invite them to register and join the Circle at the same time. You can also perform this same function from the 'Invite feature' and 'Pending Invites' from the Circle Page.