David Hoffman of Temple University Beasley School of Law recently had his research assistant update a 2006 study on citation of law-related blogs in law reviews and court opinions. He has posted the findings at Concurring Opinions. Among the top 20 cited in law reviews since 2006 are Lessig Blog by HLS professor Lawrence Lessig (which went in hibernation in 2009) and the Harvard Law School Forum on Corporate Goverance and Financial Regulation. (Credit Slips to which HLS professor Elizabeth Warren is a former contributor also made the list for blogs cited in court opinions.)
Law Librarian Lee Peoples has also looked at citation of blogs in cases (see his presentation at last year’s Future of Today’s Legal Scholarship Symposium. He also recently published an article on use of wikipedia in judicial opinions.