Who says there are no second acts on the Web? Digg, the once wildly popular site for recommending stuff on the Internet, seemed like a has-been. But new owners released a radically revised version — based on user ideas — in August. And once again, Digg is fun. The new edition has a newspaper-like front page, and ranks stories based on tweets and Facebook Likes as well as the thumbs-ups traditionally given by the site’s community.