Systemli.org runs a so-called paste service. It allows you to publicly file a text document and send the link to friends. You can choose for how long the filed text is accessible (e.g. self-destruction after first reading, after 5 minutes, ...)
This service runs the software PrivateBin, so the server admins (us) cannot read what content you file.
Of course - like with all services - the transmission is encrypted.
Onion Service Address