http://zqktlwk5ilgohy63eyrptyb4mc76bunfmxcnstkmveyjnskxkpq3b5yd.onion/wiki/Anonymous_Communications
Note that it won't take much work for someone who can monitor traffic at the server to determine your source IP, so this technique should only be used in combination with an anonymous co-location account above if true anonymity is required. And then at this point all you buy yourself is a little advance warning when the VPN service shuts you down before the Colo provider does.