Paramiko is a module for python 2.2 (or higher) that implements the SSH2 protocol for secure (encrypted and authenticated) connections to remote machines.
Unlike SSL (aka TLS), the SSH2 protocol does not require hierarchical certificates signed by a powerful central authority. you may know SSH2 as the protocol that replaced telnet and rsh for secure access to remote shells, but the protocol also includes the ability to open arbitrary channels to remote services across the encrypted tunnel -- this is how sftp works, for example.
It is written entirely in python (no C or platform-dependent code) and is released under the GNU LGPL (lesser GPL).