sshh is a set of two daemons that allows you to maintain a TCP connection if all you have available is an HTTP proxy. It is similar in functionality to httptunnel, but has a few more features. Once you have it set up, sshh will allow you to make connections forward through the proxy or backwards through it, so you can open connections in either direction.
Pagekite is software to make servers on "localhost" visible to the wider Internet. It can be used by Web developers to show off their works in progress to clients or colleagues, embedded developers who need direct access to devices in the field, or as an alternative to dynamic DNS for individuals/hobbyists who would rather host their own content than rely on 3rd party hosting. It creates and maintains a tunnel between your server on localhost and a remote "front-end" (a reverse proxy). Only the front-end has to have a visible IP address; the server itself can reside on a heavily firewalled computer, a mobile device, or even an anonymous node on the Tor network.
EARL is an HTTP tunneling proxy. It uses the POST method to transfer data. Since its datagrams are serialized objects, the traffic overhead is rather large. The datagrams are encrypted using AES to provide privacy and obfuscation to proxy maintainers. Inbound and outbound connections are possible. It is recommended to combine it with SOCKS proxies for a comfortable setup.