In Pictures: Five ways to beat the Great Firewall ...
Open proxies. These servers that anyone can access route traffic to its destination but can mask the IP address of the sender. So a person in China trying to access a forbidden site would access the IP address of a proxy server that is not blocked. If the attempted access was to a site within China restricted from the Chinese populace, requests would come from the proxy server that could be at an IP address outside China. Some options designed specifically to defeat China's censors are Freegate and Ultrasurf. It's important to pick a reliable open proxy.
In Pictures: Five ways to beat the Great Firewall of China