Paul Karlsgodt, author of ClassActionBlawg.com, has a very interesting post on Judge Sotomayor's rulings in class action cases. According to Paul, she was a member of the three-judge panels in both In re Visa Check/MasterMoney Antitrust Litigation, 280 F.3d 124 (2d Cir. 2001) and In re Initial Public Offering Securities Litigation, 471 F.3d 24 (2d Cir. 2006). (See this post for more on those cases.)
UPDATE: Legal Blog Watch has a post on Judge Sotomayor's rulings in the Visa Check and IPO cases.