The Friday night riots in the Brussels suburb of Anderlecht were incited by a blog, which was put up for the express purpose of calling upon the immigrant youth to gather and fight the skinheads. The blog, hosted on Skyrock has been taken down by the host.
As far as I can figure out, the blog is this one. For those interested in figuring out exactly what it said, Google still has it in its archive.
RTL Info reports on the blog and its comments (French)
See also: Brussels: Riots