I’m not encouraging you to join WikiLeaks. I was courious so I did a bit research. Here I share what I got and my speculation.
 
It’s said that last month a data package was provided on a BT website. It’s speculated that it includes those cables in full. Maybe it includes some tools to translate them into readable words. The volunteers worldwide downloaded them.

Regularly, the accounts of WikiLeaks on Twitter, Facebook etc. publish the messages about what will be published. Those messages can be notices to the public and also can be “orders” to its volunteers about what to do next.

When those volunteers get the message, they will work themselves to translate the related cables and publish them.

Those mirror of wikileaks are also the works of those volunteers. Sometimes, they share some script about how to relay documents between those mirror websites.

The power that makes WikiLeaks keep running under so much pressure is from the support of those anonymous volunteers.

A mirror website means a website has the same content as the master website.

Here is a tool to mirror a website:
http://rsync.samba.org/