Wikipedia, and all Wikimedia related sites, have been blocked in the People’s Republic of China since October 19, 2005. Now, there are ways for PRC-based users to access the content, such as by the trusty proxy server. One lesser known way is via a mirror inside the PRC at wikipedia.CNblog.org, but it is read-only and users cannot edit the content.
Another way for power users to access the Wikipedia site is through another server, as the “Great Firewall” does not block a certain Wikimedia address, but I will not disclose it here, so as to keep that avenue open for PRC users.
However, there is a new encyclopedia being put forth by Baidu, the most popular Chinese language search engine. If you visit baike.baidu.com, you’ll hit the new one which is quite sparse. A quick check with some online Chinese users indicate it isn’t very popular or respected. Baidu owns the copyright on the content, and articles seem to be referenced by an arbitrary number rather than by the subject title. A quick check of some articles also shows some information has been lifted from Wikipedia, without the proper GFDL notices.