If minecraft clients can be configured to use HTTP proxies, you should be able to expose a minecraft server using PageKite; PageKite can handle arbitrary TCP streams, as long as the client knows how to initialize the connection with an HTTP CONNECT.
On the PageKite side, you'd register your minecraft server as a 'raw' backend. On the minecraft client, googling suggests this might be what you need: http://www.reddit.com/r/Minecraft/comments/fr2z9/how_to_get_... - you would tell it that the PageKite front-end is an HTTP proxy.
