China now has 338m internet users - an internet penetration of 25.5%

"China has more internet users that the entire population of the United States, according to new research by the government-sanctioned China Internet Network Information Center.
The study says that at the end of June there were 338m internet users in China, a 13.4% jump since the end of 2008, and well ahead of the official US population, put at 307m by the US Census Bureau.
Rapid economic growth, and allied expansion in internet access in more areas, has fuelled the rapid rise in use of the web around China, which has a total population of 1.3bn.
That shows that internet penetration in China remains comparatively low - just 25.5% - compared to the US, where a recent study by the Pew Internet and American Life Project put the figure at over 70%."
Source: CNNIC, cited by The Guardian, 16th July 2009 (Original CNNIC report is not translated into English yet)