Do you know what today is? In case you don't, we're here to tell you: it's National Nude Day! Don't feel bad if you didn't have a party planned, because we've got the perfect celebration: a rundown of our favorite celebs showing off skin this weekend! We all know the outcome of the World Cup by now, but have you seen Rihanna's racy social media pics? The star tweeted tons of saucy shots showing off her team spirit for both Argentina and Germany! We've also got Hilary Duff in a bikini and Bar Refaeli's campaign for Passionata. Check it out in the video - and Happy National Nude Day!