I don't know a whole lot more than what you will find by clicking on this image--that Hao Wu, a Chinese blogger and filmmaker, has been detained in Beijing without charge since February 22, and that he was working on a documentary about underground Christian churches in China. There is apparently some fear that the authorities will try extract information from him that will be useful in cracking down on these churches, and that this process will not be very good for him. The source for this information is Ethan Zuckerman, founder of Global Voices (where Hao Wu blogged with the penname Tian Yi), develpment geek par excellence, friend of this blog and me through our guest bloggers Colin & Emily, and a generally brilliant and knowledgable guy.
I'm not sure what can be done at this point, how exactly awareness campaigns like this work, but I hope it does help. I know if I were making a documentary and I were detained by a government for a month, I'd want people to make some noise on my behalf. So please read up on it and consider posting this banner on your website, if you have one, and if you have more concrete ideas on how to help, please leave them in comments. FYI, the address of the Chinese embassy in the United States is: