AO3 - Next of Kin I thought I'd start with some "low hanging fruit" -- the Archive of Our Own "Next of Kin" statement. It's a pretty straightforward way to designate someone else as the caretaker of your AO3 account.
Depending on what you are interested in doing, it's nice to know that if something does happen to you and you do not have a next-of-kin, there's a clear statement that your account will not be deleted for non-use. However, if having your work outlive you is not something you want to have happen, then you should consider a next-of-kin.
Found on this page:
http://archiveofourown.org/tosV. Assorted Policies
B. Fannish next-of-kin
Registered archive users may designate a fannish next-of-kin. A next-of-kin agreement allows the transfer of content maintenance in the case of a user’s permanent incapacitation or death.
Both parties to the agreement must be registered users of the Archive.
The Archive’s role in this agreement is only to act as a facilitator. If the person designated as the fannish next-of-kin activates the agreement by sending a message to the Archive, the Archive will not do any independent investigation to confirm the necessity for the transfer.
A fannish next-of-kin agreement is confidential and accessible only by designated members of the archive team, who may only use it for purposes of implementing the agreement.( Lots more under the cut.... )