Actually I would like registered contacts to be able to fill out some custom fields in the easiest way possible. I was thinking of a "form" type link and here they can enter their contact id (to match the information with the corresponding contact) + additional information from custom fields. I don't want them to have to create an account to fill in the information, so we were thinking about using profiles, but I haven't found a way to do it.
We are using WordPress and we already have all the contacts created.