Estimating the Scope of Hate Online
Looking around, I've found this map from the folks at SPLC. Although the map uses websites to compile data, the map tracks groups, not websites.
There's also this piece from the UK reporting on the analysis by an outfit called SurfControl which sells filtering software. Here's part of the article:
"The company's research has found that the number of hate and violence Web sites has grown approximately 300 percent since 2000. At that time, the firm was tracking 2,756 Web sites. By April 2004 however, the number of Internet hate and violence sites under the company's surveillance had risen to 10,926."
Of course, they don't give any explanation about what their methodology for coming up with these numbers and given that SurfControl is selling filtering software based on a perceived threat from these groups, their estimates have to be taken with a large grain of salt.