contributed a link to Moonlight Blog, which says that "SourceForge, the world's largest development and download repository of Open Source code and applications, appears to be blocked in Mainland China. The current blocking may be related to the recent anti-China protests of Beijing Olympic Games, which will begin on 8 August. Some days before, a very popular free source code editor in SourceForge named Notepad++ start to boycott Beijing 2008. The project's developer said that the action is not against Chinese people, but against Chinese government's repression against Tibetan unrest earlier in this year. SF.net has once been banned by China in 2002. However, the ban was lifted later in 2003."
gzipped_tar adds: "As a SourceForge user in Beijing, I can confirm this first-hand. I also tried traceroute to sourceforge.net, only to find the connection being dropped at a Beijing ISP's gateway router. It appears that the projects' respective homepages are available even if they are hosted by SF, but the summary and download pages are blocked."
(As you probably know, Slashdot and Sourceforge share a corporate overlord.)