Windows/Mac: Screenstagram is an attractive, cross-platform screensaver that displays the best of Instagram on your screen.
Out of the box, Screenstagram defaults to displaying the most popular photos on Instagram. If you supply it with your login credentials, you'll also get the option to only see photos from your feed, posts that you've liked, or pictures that match specified tags. Photos slide and fade in and out of view within Screenstagram's attractive tile grid, but I wish there were a few more options to customise the layout. Even so, Screenstagram is free and worth checking out if you're in the market for a new screensaver.