Tunneling over ICMP, DNS, HTTP and HTTPS proxies

Stuck beyond a firewall, captive portal or proxy and need your ssh (or any other service)? Here's a few ways to tunnel out:

• PTunnel - Tunnel TCP using ICMP echo request and reply packets (PING), includes authentication, allows for multiple connections.
• Iodine - tunnel IPv4 data through a DNS server, allows for authentification.
• NSTX - Tunneling network packets over DNS.
  
• Corkscrew - tunneling SSH through HTTP proxies.
• httptunnel - bidirectional virtual data connection tunnelled in HTTP requests.
• gotthard - ssh through https proxy tunnel

I've already mentioned Shared Shell and such too :-).