Currently, China is blocking all VPNs at the protocol level (including corporate VPNs). However, the VPN providers listed here use stealth techniques to hide their VPN traffic.
The Great Fire website (English version) lists which sites are currently blocked in China.
There are countless VPN reviews out there, but not all VPN services are known to work within the Chinese internet infrastructure. You have to be careful when selecting your provider.
source: http://www.bestvpnprovider.com/china-vpn