From Ben Edelman, this link to a report he released today, Empirical Analysis of Google SafeSearch. “The report includes a listing of blocked URLs and of keywords that are particularly intensively filtered, and the site provides a means for users to test whether SafeSearch filtering affects a keyword or URL of interest.
See also this profile on Ben Edelman, Computer Prodigy Settles Down at HLS, from the Harvard Crimson Online.