Google self-censorship: This was circulated as a noteworthy example.

Compare the following.

Google China:
<http://images.google.cn/images?q=tiananmen>

Google the rest of the world:
<http://images.google.com/images?q=tiananmen>

Disclaimer: I don't know how significant or representative this is of the Google.cn site. (Via IPList.)

Google's official explanation (or some would say rationalization) for its China policy can be found here.