gistfile1.js

Posts.views.add("latest", function (terms) {
  return {
    options: {sort: {lastCommentedAt: -1}}
  };
});

Posts.controllers.latest = Posts.controllers.list.extend({
  view: "latest"
});

Router.route('/latest', {
  name: 'posts_latest',
  controller: Posts.controllers.latest
});