As I am currently located in China, I thought I’d give all of you some technical infos on the current censorship techniques employed here. My experience differs a little from what Wikipedia tells us.
What you see as a user:
youtube.com, facebook.com, twitter.com are all not reachable. Google.com is on and off, usually redirects to google.com.hk (which is still the less censored version of google.cn). Google.de is however available. A nice site that lets you test which web-sites are unavailable is http://www.greatfirewallofchina.org, from my experience it is reliable.
Now funny enough all things political that I checked are available, be it critical (western) newspaper sites, blogs et cetera. Even Wikipedia is available. All sites that I checked, especially Wikipedia and Google.de do offer SSL (valid!) and so looking at https://en.wikipedia.org/wiki/Tiananmen_Square_protests_of_1989 is possible (note that some sources claim that the western propaganda on this event is at least partly wrong, so don’t take this as defending the WP-article). Note also that I did not try without SSL, because I was told, that that would be detected and can get your internet service cut.
Whats going on under the hood:
Like I said, I did not experiment too much with entering sensitive terms in search engines, but regarding the web-site blocking I can say that
I currently go online trough SSH port forwarding, tunneling and proxies, will update that to proper VPN, as soon as I get the time. Anything encrypted really works, no issues with ssh and https on regular ports. OpenVPN also works…