Former Secretary of State Colin Powell got a warm welcome at Harvard this week. The retired four-star general, whose talk at the Graduate School of Education focused on the importance of mentoring, was ambushed afterward by admirer Yael Karakowsky (at right), a master’s candidate at the World’s Greatest University. . . . Perhaps following in the footsteps of Bill Parcells, who’s a big fan of the ponies, Pats coach Bill Belichick is attending the Kentucky Derby as a guest of Louisville basketball coach Rick Pitino. . . . With the Sox off Thursday, teammates Dustin Pedroia and Jacoby Ellsbury dined with friends at Nick Varano’s Strega in the North End. . . . Friday, former NBA coaches Flip Saunders and Jeff Van Gundy had lunch at Strega Waterfront.