Tor is an Onion routing system that allows you to browse the net anonymously and without interception. In Onion routing, data is repeatedly encrypted and then sent through several network nodes called onion routers. Each onion router removes a layer of encryption to uncover routing instructions, and sends the message to the next router where this is repeated. This process makes your web activity completely anonymous and makes it very difficult if not impossible to intercept your data. Sound complicated? Well it is in some respects. You can read more about it here. The reason Im telling you this is because onion encryption can be used to bypass censorship firewalls, including China's.
Before you get too exited, Tor has limitations. Due to the "detour" onion routing makes your data take, your internet speed will be significantly slower. Also, rich web applications such as Java, Flash, ActiveX, RealPlayer, Quicktime, PDF's etc will be disabled. You won't be able to use sites that completely rely on these services such as YouTube.
Here's what you will need to use Tor effectively:
Vidalia Tor Client
All of these are available for all operating systems. It is important that you download these tools before you go to China, as the websites for the Tor Project and the EFF are blocked.
Start up Vidalia, after it connects, start Firefox and toggle Torbutton. Next go to the following address:
If everything is working properly, the page will confirm your connection to the Tor network and you may begin browsing. Other applications that use the internet can also be configured to use Tor, but this requires much more technical skills. The important thing is, you have a browser.
An easier way to encrypt your web browsing is to use Hypertext Transfer Protocol Secure (HTTPS). This encrypts your connection with the website without Tor. I used this trick all the time to visit facebook at school. However, not all websites support HTTPS, but many important ones do such as Facebook, Wikipedia and Google (websites in the search results my not however). Use the HTTPS Everywhere Firefox extension above to automatically visit sites in HTTPS mode.
Since I do not live in a country with censored internet (yet) I cannot guarantee first hand that either of these will work, but its your best shot.
If Tor is not for you, an alternative way to bypass the firewall is to use a proxy site courtesy of PeaceFire. PeaceFire maintains an e-mail list it sends out weekly of different proxy sites that can be used to bypass the firewall. The proxy site will give you further instructions. You can join the e-mail list here.
UPDATE: One reader has commented that Tor is no longer effective against the Chinese fire wall. Im not sure as to what extent this is true, but as he said, a VPN is the most reliable method for bypassing the firewall. Although you will likely have to pay for it.