How the Justices Voted in Free Speech Cases, 1994–2000: "Which Justices generally take a broader view of the freedom of speech and which take a narrower view? Conventional wisdom still tells us that this should break down mostly along “liberal”/“conservative” lines, as it seemingly did during the 1970s and much of the 1980s. But it turns out that this is no longer true."
This quantitative analysis is from UCLA law professor Eugene Volokh. The top three supporters of freedom of speech turn out to be Kennedy, Thomas, and Souter. The least supportive are O'Connor, Rehnquist, and Breyer. Surprised? I was.