We've added a Like link to most of the items on the site. It's located just under the title near the author name, the Bookmark link, and the Comment link. You can like (and un-like) items. This information helps us keep the site responsive and relevant. Don't worry, we don't publish the information about who likes things: we're just interested in what works well.
In order to avoid mischief and bots, the Like feature is only available to logged-in users.
And, in a few days, there will be a new Drupal Extra that explains how we've done this.