From the Under the Jacaranda Tree Blog:
As I am writing this blog post, millions of netizens in China are celebrating the unblocking of their favourite websites, including Youtube, Picasa, Bloggers, etc. Many of these sites have been blocked since late 2008 as a part of a Chinese government sanctioned anti-vulgarity campaign.
Messages posted on Twitters suggest that blockages to Internet access have been lifted in Dalian, Changchun, Wuhan, Chongqing, Xiamen, Shenzhen, Beijing and Guangzhou.
It is not clear why or to what extent the blockage has been lifted.
Update: The outage of the GFW was temporary, according to reports from inside China, where Internet users can no longer access blocked sites. See this post from Danwei.