While, for example, OnionShare is a nice tool, for exchanging data etc., I came up a while ago with the idea to have similar capabilities, but without using Tor Browser. Onion Courier lets you exchange data with your friends, as long as the servers are running and it supports sending messages to Usenet or whitelisted email privacy providers, or Remailer Networks.
It has Middleman nodes and Guard Nodes, to form chains, like Remailers do, when sending messages. Guard nodes are useful if you do not know if your online device is compromised. In that case you prepare your messages on an offline device, encrypt the payload (with minicrypt) and then send it to the Guard node first, which decrypts the payload and forwards it to Middlemen and the final destination.
If you like Onion Courier and would like to support it feel free to run a Middleman or Guard node publicity, so that I can add it to the list.