Crypto Tunnels Wrapup

Drawbacks
TCP over TCP meltdown.
Not problematic over short periods of time.
Not problematic over decent networks.
UDP over SSH/SSL not possible natively.

SSH
OpenSSH - pretty ubiquitous on Unix-like hosts.
Requires you have shell access on/near the destination machine.

SSL/TLS
Common on much server software, especially mail protocols.
May be supported in 'wrapper mode' or STARTTLS mode.