Sina Weibo (新浪微博) is the Chinese equivalent of Twitter. It's popular in most of the Chinese-speaking world, not just mainland China.
Example of a Weibo URL: http://weibo.com/mchotdog2010 (the official account of MC HotDog
Non-redirecting Weibo URLs are changed to URLs which redirect
Update URL cleanup for Sina Weibo URLs + add them to the sidebar