Commenter htchien that Chinese users can now reach the Chinese-language Wikipedia through the site's SSL-encrypted gateway.
The standard site, zh.wikipedia.org, is still blocked. (The URL I thought led there, cn.wikipedia.org, sent me to Yahoo China last time I tried.) But for now at least, the secure URL is functional and could open the big wiki to more participation from China.
Htchein is Ted (Hsiang-Tai) Chien, who lists a position as Secretary of Wikimedia Taiwan.
UPDATE: At Ted Chien's request, I have (at least temporarily) removed the secure URL from this post. His concern is that posting the URL might tip off Chinese authorities and cause that portal to be blocked as well. I have posted aas to whether bloggers should post workarounds to online censorship. -Graham
UPDATE II: After https://secure.wikimedia.org/wikipedia/zh/wiki., I've decided that my inclination to post workarounds is the right idea. Here's the link I temporarily removed: